Newton's first law
Option 1
2. There is a bar on the table. What forces are acting on it? Why is the block at rest? Draw forces graphically.
3. There is a ball on the floor of the car. The train moves off, the ball rolls along the floor of the car. Specify the reference body with respect to which the law of inertia is true, and the reference body with respect to which this law is not satisfied.
Test 7
Newton's first law
Option 2
2. The skydiver descends, moving evenly and in a straight line. What forces are offset? Make a drawing.
3. With the help of two identical balloons, different bodies are lifted from rest. On what basis can one conclude which of these bodies has a large mass?
Test 7
Newton's first law
Option 3
2. Why, when floating timber, a large number of logs are thrown ashore at the turns of the river?
3. A fox, running away from a dog chasing her, often saves herself by making sharp sudden movements to the side just at the moment when the dog is ready to grab her with her teeth. Why does the dog miss?
Test 7
Newton's first law
Option 4
2. The ball hangs on a thread. What forces act on the ball? Why is he resting? Draw forces graphically.
3. Why does a running person, trying to quickly and steeply go around a pole or tree, wrap his arm around it?
Test 7
Newton's first law
Option 5
1. Name the bodies whose action is compensated in the following cases: 1) an iceberg floats in the ocean; 2) the stone lies at the bottom of the stream; 3) the submarine drifts uniformly and rectilinearly in the water column.
2. What will happen to the bar and why if the trolley on which it stands is sharply pulled forward? Stop abruptly?
3. Under what condition will a steamboat sailing against the current have a constant speed?
Test 7
Newton's first law
Option 6
1. Why does the mercury drop when shaking a medical thermometer?
2. The train approaches the station and slows down. In what direction at this time is it easier to drag a heavy box along the floor of the car: along the train or in the opposite direction?
3. In what ways is the ax mounted on the handle? How to explain the phenomena occurring in this case?
Test 7
Newton's first law
Option 7
1. Name the bodies, the action of which is compensated in the following cases: 1) the parachutist descends to the ground evenly and in a straight line; 2) the balloon rises evenly and in a straight line; 3) the balloon is held near the ground by ropes.
2. A load is suspended from the ceiling of the cabin of a ship moving evenly and rectilinearly. How will the cargo move relative to the cabin if the ship will: increase its speed? slow her down? turn left?
3. Why is it easier to split a log with an ax on a grand scale?
Test 7
Newton's first law
Option 8
1. Why doesn't cargo dropped from a transport aircraft fall vertically down?
2. How can you throw a drop of ink off a pen using momentum while moving?
3. An iron was placed on the book lying on the table. The book remains at rest despite the fact that the weight of the iron acts on it. Is there a contradiction here with Newton's first law?
Test 7
Newton's first law
Can not. Due to the force of friction, its movement slows down. Faithful about the Earth and things related to it. Not performed with respect to the wagon and related items. |
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1. The legs of a person stop along with the boat, and the upper part, due to the law of inertia, continues to move. 2. Compensate for gravity and air resistance.
3. A body of greater mass rises more slowly. |
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The driver cannot immediately stop the car due to the law of inertia. At the turns of the river, the logs continue their rectilinear motion and are thrown ashore. The fox abruptly changes the direction of movement, and its tail continues to move in the same direction. The dog misses, rushing towards the tail. |
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Can not. Due to the forces of friction, its movement slows down.
To change the direction of movement, the action of some force directed away from the direction of movement is necessary. Such a force is the force with which the tree acts on a person. |
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In all cases, the actions of the Earth and water are compensated. If you pull forward sharply, the bar will fall back from the cart. If you stop the cart abruptly, the block will fall forward. If the own speed of the ship will be greater than the speed of the current and will be directed opposite to the direction of the current. |
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The thermometer is sharply slowed down, and the mercury in the capillary continues to move due to inertia. It's easier on the train. Hit with a hammer on the opposite end of the handle. The ax remains at rest, and the handle moves in the butt of the ax. |
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1. In all cases, these bodies are the Earth and air. 2. When the speed increases, the load will deviate in the opposite direction; when slowing down - deviate in the direction of movement; when turning left, the load will deflect to the right. 3. When braking against a tree, the ax continues to move inside the wood due to inertia. |
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1. The load continues to move by inertia in the direction of the aircraft. 2. Move the pen quickly and stop abruptly. 3. There is no contradiction, since all the forces acting on the book are compensated. |
Test 8
Newton's laws
Option 1
1. Can a puck thrown by a hockey player move evenly across the ice? Explain answer.
2. Several forces act on the body. What is the direction of the acceleration of the body caused by the action of these forces?
A. In the direction of the resultant.
B. In the direction of the greater of the forces.
B. Opposite to the direction of the resultant.
3. Why does the boat not budge when the person in it pushes on the side, and starts moving if the person gets out of the boat and pushes it with the same force?
Test 8
Newton's laws
Option 2
1. There is a bar on the table. What forces are acting on it? Why is the block at rest? Draw forces graphically.
2. What is body weight?
A. Body weight.
B. The amount of matter contained in the body.
B. A measure of the inertia of a body.
Test 8
Newton's laws
Option 3
1. There is a ball on the floor of the car. The train moves off, the ball rolls along the floor of the car. Specify the reference body with respect to which the law of inertia is true, and the reference body with respect to which this law is not fulfilled.
3 . A mosquito hit the windshield of a moving car. Compare the forces acting on the mosquito and the car during the impact.
Test 8
Newton's laws
Option 4
1. Why is it difficult for a person standing in a moving boat to maintain their previous position if the boat suddenly stops?
2. One force acts on the body. What is the direction of the acceleration caused by this force?
A. Co-directed with the acting force.
B. Opposite direction of force.
B. Along the line of action of the force, in the direction of its action.
3. A motor ship in a collision with a boat can sink it without any damage to itself. How does this agree with the equality of the moduli of the interaction forces?
Test 8
Newton's laws
Option 5
1. The skydiver descends, moving evenly and in a straight line. What forces are offset? Make a drawing.
2. How does the acceleration of a body depend on the force applied to it? Which statement is incorrect?
A. The modulus of acceleration is directly proportional to the modulus of the force acting on the body.
B. The direction of acceleration of the body coincides with the direction of the force acting on this body.
B. The acceleration of a body does not depend on the force applied to it.
3. Is it possible to sail on a sailboat by directing a stream of air onto the sails from a powerful fanlocated on the boat? What happens if you blow past the sail?
Test 8
Newton's laws
Option 6
1. With the help of two identical balloons, different bodies are lifted from rest. On what basis can one conclude which of these bodies has a large mass?
2. Are the formulas equivalent? 
A. Only formulas 1) and 2) are equivalent.
B. All formulas are not equivalent.
B. All formulas are equivalent.
Test 8
Newton's laws
Option 7
1. Why can't you cross the street in front of a nearby vehicle? What is the reason that the driver cannot immediately stop the car?
2. Does a constant force cause a constant acceleration?
A. Under the action of a constant force, the acceleration gradually increases.
B. . Under the action of a constant force, the acceleration gradually decreases.
B. Under the action of a constant force, the body moves with constant acceleration.
Test 8
Newton's laws
Option 8
1. Why, when floating timber, a large number of logs are thrown ashore at the turns of the river?
2. How to measure body weight by weighing?
A. Make a measurement using any dynamometer.
B. Make a measurement using electronic scales.
B. Graduate the scale of the spring balance using a weight of known mass as a standard.
3 . The book lying on the table presses on him with some force. The table acts on the book with the same upward force. Can you find the resultant of these forces?
Test 8
Newton's laws
Option 9
1. A fox, running away from a dog chasing her, often saves herself by making sharp sudden movements to the side just at the moment when the dog is ready to grab her with her teeth. Why does the dog miss?
2. What is the formula for Newton's second law?
A. font-size:12.0pt;letter-spacing:-.05pt"> B. font-size:12.0pt;letter-spacing:-.05pt">C.font-size:12.0pt;letter-spacing:- .05pt">3.A mosquito hit the windshield of a moving car. Compare the forces acting on the mosquito and the car during the impact.
Test 8
Newton's laws
Option 10
1. Can the car move evenly on a horizontal highway with the engine off? Explain the answer.
2. Does the direction of motion of the body always coincide with the direction of the force acting on the body?
A. Yes.
B. It depends on body weight.
B. No.
3 . A motor ship in a collision with a boat can sink it without any damage to itself. How does this agree with the equality of the moduli of the interaction forces?
Test 8
Newton's laws
Option 11
1. The ball hangs on a thread. What forces act on the ball? Why is he resting? Draw forces graphically.
2. In what frames of reference is Newton's second law valid?
A. Only in non-inertial frames of reference.
B. In any reference systems.
B. Only in inertial frames of reference.
3 . Is it possible to sail on a sailboat by directing a stream of air from a powerful fan located on the boat onto the sails? What happens if you blow past the sail?
Test 8
Newton's laws
Option 12
1. Why does a running person, trying to quickly and steeply go around a pole or tree, wrap his arm around it?
2. How is Newton's second law formulated?
A. The resultant of all forces applied to the body is equal to the product of the body's mass and its acceleration.
B. The force applied to the body is equal to the product of the body's mass and its acceleration.
B. The resultant of all forces applied to the body is equal to the ratio of the mass of the body to its acceleration.
3. What can be said about the acceleration that the Earth receives when interacting with a person walking on it? Justify the answer.
Test 8
Newton's laws
Option 13
1. Name the bodies whose action is compensated in the following cases: 1) an iceberg floats in the ocean; 2) the stone lies at the bottom of the stream; 3) the submarine drifts uniformly and rectilinearly in the water column.
2. How does the force of gravity acting on a body depend on its mass?
A. The force of gravity acting on a body does not depend on its mass.
B. The force of gravity acting on a body is inversely proportional to its mass.
B. The force of gravity acting on a body is directly proportional to its mass.
3 . Why does the boat not move when the person in it pushes on the side, and starts moving if the person gets out of the boat and pushes it with the same force?
Test 8
Newton's laws
Option 14
1. What will happen to the bar and why if the trolley on which it stands is sharply pulled forward? Stop abruptly?
2. How does the acceleration modulus depend on the force modulus?
A. The modulus of acceleration is directly proportional to the modulus of force.
B. The modulus of acceleration does not depend on the modulus of force.
B. The modulus of acceleration is inversely proportional to the modulus of force.
3. The book lying on the table presses on him with some force. The table acts on the book with the same upward force. Can you find the resultant of these forces?
Test 8
Newton's laws
Option 15
1. Under what condition will a steamboat sailing against the current have a constant speed?
2. How to find the resultant?
A. Find the algebraic sum of all forces acting on the body.
MOU secondary school No. 5
Multi-level independent work in physics.
Grade 9
City of Zheleznodorozhny. 2011
FIRST LEVEL - the level of mandatory minimum training. Successful completion of tasks at this level indicates the compliance of this student with the state requirements of the standard for the course of physics in grades 7 and 8. They are required by all students. At this level, the student should be able to solve problems using 1 basic formula.
SECOND LEVEL - somewhat difficult level.
It is focused mainly on the achievement by students of the required level of training in physics. Along with tasks aimed at developing basic skills, it contains simple tasks that require ingenuity and ingenuity.
Tasks at this level make it possible to reveal the ability of students to apply knowledge according to a model, to solve calculation problems according to a rule or an algorithm using 1-2 basic formulas.
THIRD LEVEL - elevated level.
It is designed for students with a good background in physics, which gives them the opportunity to quite intensively master the basic knowledge and skills and learn how to apply them in a variety of complicated situations.
Tasks of this level allow to reveal the ability of students to apply knowledge in a changed, non-standard situation, to solve calculation problems using more than 2 basic formulas.
"Material point. Trajectory, path, movement.
First level .
No. 1. In which of the following cases can a body be considered a material point?
A. The moon revolves around the earth.
B. The spacecraft makes a soft landing on the Moon.
Q. Astronomers observe an eclipse of the moon.
No. 2. The girl threw the ball up and caught it. Assuming that the ball has risen to a height of 2 m, find the modulus of the ball's displacement.
A. 2 m.
B. 4 m.
V. 0 m.
No. 3. Indicate what is taken as the body of reference when they say that the conductor is walking along the car at a speed of 3 km / h.
No. 4. According to a given trajectory of the body
find its displacement,
If the starting point of the trajectory is A, and the end point is C.
Solve the problem graphically.
Second level.
№ 1. Does the trajectory of the body's motion depend on the frame of reference?
No. 2. The helicopter, flying in a horizontal flight in a straight line for 30 km, turned at an angle of 90 and flew another 40 km. Find the path and movement module of the helicopter.
No. 3. Draw schematically the trajectory of the movement of the points of the propeller of the aircraft relative to the pilot.
No. 4. The ball fell from a height of 4 m, bounced off the ground and was caught at half the height. What is the path and modulus of the ball.
Third level.
No. 1. Draw the trajectory of movement, in which the displacement module is 10 cm, and the path is 30 cm.
No. 2. The motorboat passed along the lake in the north-east direction for 2 km, and then in the northern direction for another 1 km. Find the module and the direction of movement by geometric construction.
№ 3. Give an example of movement, the trajectory of which in one frame of reference is a straight line, and in another - a circle.
No. 4. The tourist went from village A to village B. First, he walked 3 km to the north, then turned west and walked another 3 km, and the last kilometer he moved along a country road going north. What path did the tourist travel and what is his module of movement? Draw a trajectory of movement.
Independent work on the topic
"Rectilinear Uniform Motion".
First level.
No. 1. A train 240 m long, moving uniformly, passed the bridge in 2 minutes. What is the speed of the train if the bridge is 360 m long?
No. 2. The car traveled 900 m in the first 10 minutes. What distance will it cover in 0.5 hours, moving at the same speed?
Second level.
No. 1. When moving along the OX axis, the coordinate of the point changed in 5 s from the value x 1 \u003d 10 m to the value x 2 \u003d - 10 m. Find the speed module of the point and the projection of the velocity vector on the OX axis. Write down the dependence formula x( t ). Consider the speed constant.
No. 2. Two bodies move along the OX axis, the coordinates of which change according to the formulas: x 1 \u003d 10 +2 t and x 2 \u003d 4 + 5 t . How do these bodies move? At what point in time will the bodies meet? Find the coordinate of the meeting point.
Third level.
No. 1. The movement of a material point in the XOY plane is described by the equations x=2 t , y=4-2 t . Find the starting coordinates of the moving point. Build a trajectory.
No. 2. The distance between two piers is 10 minutes downstream and 30 minutes upstream. How long will it take for a lifebuoy that has fallen into the water to float downstream?
Independent work on the topic
"Rectilinear uniformly accelerated motion".
First level.
No. 1. With what acceleration does a tram starting off move if it picks up speed of 36 km / h in 25 s?
No. 2. The train, moving away from the station, picks up a speed of 15 m / s in 1 minute. What is its acceleration?
Second level.
No. 1. After 10 seconds, the car acquires a speed of 20 m / s. With what acceleration was the car moving? After what time will its speed become equal to 108 km/h if it moves with the same acceleration?
No. 2. The body moves with uniform acceleration. How long will it take to move in the same direction. What and at the initial moment, if 0x \u003d 20 m / s, and x \u003d -4 m / s 2?
Third level.
No. 1. The body moves in a straight line. At the beginning and at the end of the movement, the speed modulus is the same. Could the body move with constant acceleration?
No. 2. Two trains go towards each other: one will accelerate in the direction to the north; the other slows down in a southerly direction. How are train accelerations directed?
Independent work on the topic
"Displacement in rectilinear uniformly accelerated motion."
First level.
No. 1. A cyclist moving at a speed of 3 m/s starts downhill with an acceleration of 0.8 m/s 2 . Find the length of the mountain if the descent took 6 s.
No. 2. The car increased its speed from 36 km / h to 54 km / h in 4 s. How far did the car travel during this time?
Second level.
No. 1. The car, having stopped in front of a traffic light, then picks up a speed of 54 km / h on a path of 50 m. With what acceleration should it move? How long will the acceleration take?
No. 2. A bullet flying at a speed of 400 m / s hits an earthen rampart and penetrates it to a depth of 36 cm. How long did the bullet move inside the rampart? With what acceleration? What was its speed at a depth of 18 cm?
Third level.
No. 1. With uniformly accelerated movement, the point passes in the first two equal consecutive periods of time, 4 s each, the paths are 24 m and 64 m. Determine the initial speed and acceleration of the moving point.
No. 2. Having noticed the traffic inspector, the driver brakes sharply. The car passed point A at a speed of 144 km / h, and point B - already at a speed of 72 km / h. At what speed was the car moving in the middle of segment AB?
Independent work on the topic
"Newton's Laws".
Option 1.
First level.
No. 1. There is a bar on the table. What forces are acting on it? Why is the block at rest? Draw forces graphically.
No. 2. What force imparts an acceleration of 4 m / s 2 to a body weighing 5 kg?
No. 3. Two boys pull the cord in opposite directions, each with a force of 200N. Will the cord break if it can withstand a load of 300 N?
Second level.
No. 1. With the help of two identical balloons, different bodies are lifted from rest. On what basis can one conclude which of these bodies has a large mass?
No. 2. Under the action of a force of 150N, the body moves in a straight line so that its coordinate changes according to the law x \u003d 100 + 5 t +0.5 t2 . What is the body weight?
No. 3. An incomplete glass of water is balanced on the scales. Will the balance of the balance be disturbed if a pencil is immersed in water and held in the hand without touching the glass?
Third level.
No. 1. The frame of reference is connected to the car. Will it be inertial if the car moves: 1) evenly and straight on a horizontal highway; 2) accelerated along a horizontal highway; 3) evenly turning; 4) evenly uphill; 5) evenly from the mountain; 6) accelerated from the mountain?
No. 2. A body at rest with a mass of 400 g under the action of a force of 8 N acquired a speed of 36 km / h. Find the path that the body has traveled.
No. 3. A horse pulls a loaded cart. According to Newton's third law, the force with which the horse pulls the cart is equal to the force with which the cart pulls the horse. Why does the cart follow the horse?
Independent work on the topic
"Newton's Laws".
Option 2.
First level.
No. 1. What will happen to the bar and why, if the trolley on which it stands is sharply pulled forward? Stop abruptly?
No. 2. Determine the force under the influence of which a body of mass 500 g receives an acceleration of 2 m / s.
№ 3. What can be said about the acceleration that the Earth receives when interacting with a person walking on it? Justify the answer.
Second level.
No. 1. A fox, running away from a dog chasing her, often saves herself by making sharp sudden movements to the side just at the moment when the dog is ready to grab her with her teeth. Why does the dog miss?
No. 2. A skier weighing 60 kg, having a speed of 10 m/s at the end of the descent from the mountain, stopped 40 s after the end of the descent. Determine the modulus of the force of resistance to movement.
No. 3. Is it possible to sail on a sailboat by directing air flow from a powerful fan on the boat to the sails? What happens if you blow past the sail?
Third level.
No. 1. The car moves uniformly along the ring road. Is the frame of reference associated with it inertial?
No. 2. A body weighing 400 g, moving in a straight line with a certain initial speed, acquired a speed of 10 m/s in 6 s under the action of a force of 0.6 N. Find the initial speed of the body.
No. 3. A rope is thrown over a fixed block. A person hangs on one end of the rope, holding on with his hands, and a load on the other. The weight of the load is equal to the weight of the person. What happens if a person pulls himself up the rope on his hands?
Independent work on the topic
"Free fall".
Option 1.
First level.
No. 1. A body falls without initial velocity. What is its speed after 2 seconds of fall?
№ 2. How long will it take the ball, which began its fall without initial speed, to cover a distance of 20 m?
Second level.
No. 1. How long did the body fall without initial speed, if in the last 2 s it has traveled 60 m?
No. 2. A body falls from a height of 100 m without initial velocity. What is the distance traveled by the body during the first and last seconds of its fall?
Third level.
No. 1. A body falls freely from a height of 27 m. Divide this height into three parts so that the passage of each of them takes the same time.
No. 2. Two loads were dropped from a helicopter without an initial speed, and the second one was 1 s later than the first. Determine the distance between the loads after 2 s and 4 s after the start of the movement of the first load.
Independent work on the topic
"Free fall".
Option 1.
First level.
No. 1. A ball was fired vertically upwards from a spring pistol, which rose to a height of 5 m. With what speed did the ball fly out of the pistol?
No. 2. The ball is thrown vertically upwards with a speed of 18 m/s. What movement did he make in 3 seconds?
Second level.
No. 1. The boy threw the ball vertically upwards and caught it after 2 s. What is the height of the ball and what is its initial speed?
No. 2. Throwing the ball vertically upwards, the boy tells him the speed is 1.5 times greater than the girl. How many times higher will the ball thrown by the boy rise?
Third level.
Two balls are thrown vertically upwards with an interval of 1 s. The initial speed of the first ball is 8 m/s, and the second - 5 m/s. At what height will they meet?
No. 2. Two balls are simultaneously thrown from a tower 20 m high: one is thrown up at a speed of 15 m/s, the other is thrown down at a speed of 5 m/s. What is the time interval separating the moments of their fall to the ground?
Independent work on the topic
"Gravity and free fall acceleration".
№ 1. What is the force of gravitational attraction between two identical billiard balls at the moment of collision? The mass of each ball is 200 g, the diameter is 4 cm.
№ 2. At what distance will the force of attraction between two bodies weighing 1000 kg each be equal to 6.6710 -9 N?
Second level.
No. 1. At what distance from the surface of the Earth is the force of attraction of the spacecraft to the Earth 100 times less than on its surface?
No. 2. Determine the acceleration of free fall at a height equal to the radius of the Earth.
Third level.
No. 1. The mass of the orange planet is 5 times the mass of the Earth. What is the radius of this planet if the free fall acceleration on its surface is the same as on Earth?
No. 2. A body weighing 1 kg is attracted to the moon with a force of 1.7 N. Assuming that the average density of the moon is 3.510 3 kg / m 3, determine the radius of the moon.
Independent work on the topic
"The movement of artificial satellites".
First level.
No. 1. Calculate the orbital speed of the satellite at an altitude of 300 km above the Earth's surface.
No. 2. Calculate the first escape velocity for Venus. Consider the radius of Venus equal to 6000 km, and the acceleration of free fall 8.4 m/s 2 .
Second level.
No. 1. The moon moves around the Earth in a circular orbit at a speed of 1 km / s, while the radius of its orbit is 384,000 km. What is the mass of the earth?
No. 2. Can a satellite revolve around the Earth in a circular orbit at a speed of 1 km / s? Under what condition is this possible?
Third level.
No. 1. The spacecraft went into a circular orbit with a radius of 10,000,000 km around the star he discovered. What is the mass of the star if the period of revolution of the ship is 628000 s?
No. 2. An artificial satellite revolves in a circular orbit around the Earth at a speed of 6 km / s. After the maneuver, it moves around the Earth in another circular orbit at a speed of 5 km/s. How many times have the radius of the orbit and the period of revolution changed as a result of the maneuver?
Independent work on the topic
"The Law of Conservation of Momentum".
First level.
No. 1. The movement of a material point is described by the equation: x=20+2t-t 2 . Its mass is 4 kg, find the impulse after 1 s and 4 s after the start of the time countdown.
No. 2. A car weighing 30 tons. Moving horizontally at a speed of 1.5 m / s, it automatically couples on the go with a stationary car weighing 20 tons. At what speed does the hitch move?
Second level.
No. 1. An icebreaker with a mass of 5000 tons. Moving with the engine turned off at a speed of 10 m / s, it collides with a stationary ice floe and moves it ahead of itself. The speed of the icebreaker at the same time decreased to 2 m/s. Determine the mass of the ice.
No. 2. A grenade flying in a horizontal direction at a speed of 10 m / s. Exploded into two fragments weighing 1 kg and 1.5 kg. The speed of the larger fragment remained horizontal after the explosion and increased to 25 m/s. Determine the magnitude and direction of the velocity of the smaller fragment.
Third level.
No. 1. A rope is selected from the boat, fed to the longboat. The distance between them is 55 m. Determine the paths traveled by the boat and longboat before they meet. The mass of the boat is 300 kg, the mass of the launch is 1200 kg. Ignore water resistance.
No. 2. Can it be argued. What is the momentum of a body relative? Justify the answer.
Independent work on the topic
"Propagation of Waves".
Option 1.
No. 1 The period of oscillation of water particles is 2 s. And the distance between adjacent wave crests is 6 m. Determine the propagation speed of these waves.
No. 2. At what distance from a sheer cliff is a person. If I clap my hands, after 1 second he heard the echo of the clap?
Second level.
No. 1. Why can transverse and longitudinal waves propagate in solids?
No. 2. 6 crests of waves passed by a stationary observer in 20 s, starting from the first one. What is the wavelength and period of oscillation if the wave speed is 2 m/s?
Third level.
No. 1. Why are the bass strings of guitars braided with wire?
No. 2. An explosion was made in the ocean at a shallow depth. The hydroacoustics of the ship, located at a distance of 2.25 km from the explosion site, recorded two sound signals, the second one 1 s after the first. What is the depth of the ocean in this area?
Option 2.
First level.
#1 What is the wavelength of a 200 Hz sound wave in air?
No. 2. A thunderclap sounded 15 seconds after the lightning flash. At what distance from the observer did the lightning discharge occur?
Second level.
№ 1. What is the relationship between the wavelength, the speed of wave propagation, the frequency of oscillations?
No. 2. The sound of an explosion produced in the water near the surface, the instruments installed on the ship and receiving the sound in the water, were registered 45 seconds earlier than it came through the air. At what distance from the ship did the explosion occur?
Third level.
№ 2. When the boat moves in the direction of wave propagation, the waves hit the hull with a frequency of 1 Hz, and when moving towards the waves - with a frequency of 3 Hz. With what speed does the boat move relative to the shore if the water particles oscillate with a frequency of 1 Hz, and the distance between the wave crests is 5 m?
Independent work on the topic
"A magnetic field. Vector of magnetic induction.
First level.
No. 1. A straight conductor with a current perpendicular to its magnetic lines is placed in a magnetic field. How will the modulus of the magnetic induction vector change with an increase in current strength by 2 times? With a decrease in the length of the conductor by 1.5 times?
№ 2. What can be judged by the pattern of magnetic field lines?
Second level.
No. 1. What is the induction of the magnetic field in, in which a force of 0.05 N acts on a conductor with a current of 25 A? The length of the active part of the conductor is 5 cm. The direction of the induction and current lines are mutually perpendicular.
No. 2. A magnetic field with an induction of 10 mT acts on a conductor in which the current strength is 50 A, with a force of mN. Find the length of the conductor if the field induction lines and the current are mutually perpendicular.
Third level.
No. 1. Current flows in two parallel conductors. The direction of which is indicated by arrows. How do conductors interact? Prove the correct answer.
No. 2. Between the poles of an electromagnet in a horizontal magnetic field there is a straight conductor located horizontally and perpendicular to the magnetic field. What current must flow through the conductor to destroy the tension in the flexible wires supporting it? The magnetic field induction is equal to 0.01 T, the mass per unit length of the conductor=0.01 kg/m.
Solve the problem graphically.
When completing tasks 2–5, 8, 11–14, 17–18 and 20–21, write down one number in the answer field, which corresponds to the number of the correct answer. The answer to tasks 1, 6, 9, 15, 19 is a sequence of numbers. Write down this sequence of numbers. Answers to tasks 7, 10 and 16 write down as a number, taking into account the units indicated in the answer.
1
The load is lifted using a movable block with a radius R. Establish a correspondence between physical quantities and the formulas by which they are determined. For each concept in the first column, select the appropriate example from the second column.
2
A ball rolls down an inclined plane with uniform acceleration from rest. The initial position of the ball and its position every second after the start of movement are shown in the figure.
What distance will the ball cover in the fourth second from the start of the movement?
3
Three solid metal balls of the same volume, lead, steel and aluminum, fall from the same height with no initial velocity. Which ball will have the maximum kinetic energy at the moment it hits the ground? Consider air resistance to be negligible.
1) lead
2) aluminum
3) steel
4) the values of the kinetic energy of the balls are the same
4
The figure shows the dependence of the amplitude of the steady harmonic oscillations of a material point on the frequency of the driving force. At what frequency does the resonance occur?
5
Water is poured into two glass cylindrical vessels to the same level.
Compare the pressures (p 1 and p 2) and the pressure forces (F 1 and F 2) of water at the bottom of the vessel.
1) p 1 \u003d p 2; F 1 = F 2
2) p1< p 2 ; F 1 = F 2
3) p 1 = p 2; F1 > F2
4) p 1 > p 2; F1 > F2
6
A tied inflated rubber ball was placed under the bell of the air pump. Then, under the bell, they began to additionally pump air. How do the volume of the balloon and the density of the air in it change during the pumping of air?
For each value, determine the appropriate nature of the change:
1) increases
2) decreases
3) does not change
Write down the selected numbers for each physical quantity. Numbers in the answer may be repeated.
7
1 m 3 of water was slowly pumped out of the well with a pump. The work done in this case is 60 kJ. What is the depth of the well?
Answer: ______ m
8
Hot water is being poured into a thin glass beaker. Which of the available spoons (aluminum or wooden) is recommended to be lowered into the glass before pouring water so that the glass does not crack?
1) aluminum, since the density of aluminum is greater
2) wooden, since the density of the tree is less
3) aluminum, since the thermal conductivity of aluminum is greater
4) wooden, since the thermal conductivity of wood is less
9
The figure shows graphs of the time dependence of the temperature of two different substances that release the same amount of heat per unit time. Substances have the same mass and are initially in a liquid state.
From the statements below, choose two correct ones and write down their numbers.
1) The crystallization temperature of substance 1 is lower than that of substance 2.
2) Substance 2 completely passes into the solid state when the crystallization of substance 1 begins.
3) The specific heat of crystallization of substance 1 is less than that of substance 2.
4) The specific heat capacity of substance 1 in the liquid state is greater than that of substance 2
5) During the time interval 0-t 1, both substances were in a solid state.
10
Mixed two portions of water: 1.6 liters at a temperature of t 1 = 25 ° C and 0.4 liters at t 2 = 100 ° C. Determine the temperature of the resulting mixture. Neglect heat exchange with the environment.
Answer: _____ °C
11
Which of the following substances is a conductor of electric current?
1) sugar solution
3) sulfuric acid solution
4) distilled water
12
The figure shows a diagram of connecting three identical lamps to a DC voltage network.
Lamp(s) will be lit at maximum intensity
13
A magnet is inserted into a coil connected to a galvanometer. The magnitude of the inductive current depends
A. from whether a magnet is brought into the coil or taken out of it
B. on which pole the magnet is inserted into the coil
The correct answer is
1) only A
2) only B
4) neither A nor B
14
Rays a and b from the source S are incident on the lens. After refraction in the lens, the rays
1) will go parallel to the main optical axis
2) intersect at point 1
3) intersect at point 2
4) intersect at point 3
15
The nickel-plated coil of the hot plate was replaced with a nichrome coil of the same length and cross-sectional area. Establish a correspondence between physical quantities and their possible changes when the tile is connected to the electrical network.
PHYSICAL QUANTITY
A) electrical resistance of the coil
B) the strength of the electric current in the spiral
B) electric current power consumed by the tiles
NATURE OF THE CHANGE
1) increased
2) decreased
3) has not changed
| BUT | B | IN |
16
Two resistors connected in series are connected to the battery. The resistance of the first resistor is 4 times the resistance of the second resistor: R 1 = 4R 2. Find the ratio of the amount of heat released on the first resistor to the amount of heat released on the second resistor in the same period of time.
Answer: _____
17
What chemical element is formed during a nuclear reaction
18
Record the measurement of atmospheric pressure with an aneroid barometer. The measurement error is taken equal to the scale division.
1) (107 ± 1) kPa
2) (100.7 ± 0.1) kPa
3) (750 ± 5) kPa
4) (755 ± 1) kPa
19
Using a glass of hot water, a thermometer and a clock, the teacher conducted experiments in class to study the temperature of cooling water over time. The table presents the results of the research.
From the proposed list, select two statements that correspond to the experiments. List their numbers.
1) The change in the temperature of the cooling water is directly proportional to the observation time.
2) The rate of cooling of water decreases as the water cools.
3) As the water cools, the rate of evaporation decreases.
4) Water cooling was observed for 46 minutes.
5) In the first 5 minutes, the water cooled down to a greater extent than in the next 5 minutes.
Read the text and complete tasks 20–22.
Superfluidity
Superfluidity of liquid helium is another unusual quantum mechanical phenomenon that occurs at temperatures close to absolute zero. If you cool gaseous helium, then at a temperature of -269 ° C, it will liquefy. If this liquid helium continues to be cooled, then at a temperature of -271 ° C, its properties will suddenly change. In this case, macroscopic phenomena occur that do not fit into the framework of conventional ideas. For example, a vessel partially filled with this strange modification of liquid helium (called helium II) and left uncovered will soon empty itself. This is explained by the fact that liquid helium rises along the inner wall of the vessel (regardless of its height) and overflows over the edge outward. For the same reason, the opposite phenomenon can also occur (see Fig.). If an empty glass is partially immersed in liquid helium, it will quickly fill the glass to the liquid level outside. Another strange property of pure liquid helium II is that it does not transfer forces to other bodies. Could a fish swim in liquid helium II? Of course not, because she would freeze. But even an imaginary ice-free fish would not be able to swim, because it would have nothing to push off from. She would have to rely on Newton's first law.
Formulating these amazing properties of liquid helium II in the language of mathematics, physicists say that its viscosity is zero. It remains a mystery why the viscosity is zero. Like superconductivity, the amazing properties of liquid helium are now under intense investigation. Significant progress has been made towards a theoretical explanation of the superfluidity of liquid helium II.
20
At what temperature does helium go into a superfluid state?
4) is fluid at any temperature
1. The ball moves under the action of a force constant in magnitude and direction. Choose the correct statement:
A. The speed of the ball does not change.
B. The ball moves uniformly.
V. Sharik moves with constant acceleration.
2. HOW does a ball of mass 500 g move. under the action of a force of 4 N?
A. With an acceleration of 2 m/s (squared)
B. With constant speed 0.125m/s.
V. With constant acceleration 8m/s(squared)
3. In what cases below are we talking about the movement of bodies by inertia?
A. The body lies on the surface of the table.
B. After turning off the engine, the boat continues to move on the surface of the water
B. The satellite moves in orbit around the Sun.
4.a) why is Newton's first law called the law of inertia?
b. How does a body move if the vector sum of the forces acting on it is zero?
c. A mosquito hit the vector glass of a moving car. Compare the forces acting on the mosquito and the car during the impact.
5.a. Under what condition can a body move uniformly and rectilinearly?
b. With the help of two identical balloons, different bodies are crushed from a state of rest. By what sign can one conclude which of these bodies has a greater mass?
c. The ball hits the window glass. Which of the bodies (ball or glass) is affected by a large force upon impact?
7.a. There is a bar on the table. What forces act on it? Why is the bar at rest?
b. With what acceleration does a jet aircraft with a mass of 60 tons move during takeoff, if the thrust force of the engines is 90 kN?
c. A motor ship, in a collision with a boat, can sink it without any damage to itself. How does this agree with the equality of the modules of the interaction forces?
8.a. In what ways is the ax planted on the handle? How to explain the phenomena occurring in this case?
b. What force informs a body with a mass of 400 g. acceleration 2 m/s (square)?
c. Two boys pull the cord in opposite directions, each with a force of 100N. Will the cord break if it can withstand a load of 150N?
Pa. Determine the mass of helium at which the balloon lifts itself. The temperature of helium and the surrounding air is the same and equal to 0 С.
1) From the equations given below, select the numbers of those that describe the state of rest of the body:1) x \u003d -2 + t2; 2) x = 5; 3) x = 2/t; 4) x = 2-t; 5) Vx = 5+2t; 6) Vx = 5; 7) Vx = -5- 2t; 8) Vx = -2+t2;
3. What should be the length of the runway if the aircraft to take off must acquire a speed of 240 km / h, and the acceleration time is approximately 30 s?
4. The equation of motion has the form: x = 3 + 2t - 0.1 t2. Determine the movement parameters, plot Vx (t) and determine the path traveled by the body in the second second of movement.
5. The cyclist and motorcyclist start moving simultaneously from rest. The acceleration of a motorcyclist is 2p greater than that of a cyclist. How many times faster will a motorcyclist develop in the same time?
6. The range of a body thrown horizontally at a speed of 20 m/s is equal to the height of the throw. From what height was the body dropped?
7. With uniform motion in a circle, the body travels 5 m in 2 s. What is the centripetal acceleration of the body if the period of revolution is 5 s?
HELP ME SOMETHING
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Introduction
Relevance
Are you familiar with the situation when, after a birthday or some other holiday, a lot of balloons appear in the house? At first, the children are happy with the balls, they play with them, but soon they stop paying attention to them and the balls only get under their feet. What to do with them so that they do not lie without any purpose, but bring benefits? Of course, use in cognitive activities!
In general, balloons are an excellent material for demonstrating various experiments and models. It would be interesting to write a book in which all physical concepts will be explained through them. In the meantime, I want to invite you to conduct more than a dozen experiments from different fields of science - from thermodynamics to cosmology - in which the props are common: balloons.
Target: Explore balloons as an invaluable material at hand for observing physical phenomena and staging various physical experiments.
Tasks:
Learn about the history of balloons.
Set up a series of experiments with balloons.
Analyze the observed phenomena and formulate conclusions.
Create a multimedia presentation.
Object of study: balloon.
Research methods:
. Theoretical: study of literature on the research topic.
. Comparative-comparative.
. Empirical: observation, measurement.
. Experimental-theoretical : experiment, laboratory experiment.
Material of this study are Internet sources, teaching aids in physics, physics textbooks, problem books, archive data and other reference literature.
Practical significance: The results of the study can be used in physics lessons, at conferences, when reading elective courses and at extracurricular activities.
Theoretical part
The history of the creation of balloons
Looking at modern balloons, many people think that this bright, pleasant toy has only recently become available. Some, more knowledgeable, believe that balloons appeared somewhere in the middle of the last century, simultaneously with the beginning of the technical revolution. Actually it is not. The history of balloons filled with air began much earlier. Only the ancestors of our balls looked completely different from what they are now. The first references to the manufacture of balloons flying in the air that have come down to us are found in Karelian manuscripts. They describe the creation of such a ball, made from the skin of a whale and a bull. And chronicles of the 12th century tell us that in the Karelian settlements almost every family had a balloon. Moreover, it was with the help of such balls that the ancient Karelians partially solved the problem of off-road - the balls helped people overcome the distances between settlements. But such journeys were quite dangerous: the shell of animal skins could not withstand air pressure for a long time - that is, in other words, these balloons were explosive. And so, in the end, only legends remained of them. But less than 7 centuries have passed since that semi-mythical era, when rubber balloons were invented in London by Professor Michael Faraday. The scientist studied the elastic properties of rubber - and built two "cakes" from this material. In order for the "cakes" not to stick together, Faraday treated their inner sides with flour. And after that, with his fingers, he glued their raw, remaining sticky edges. The result was something like a bag that could be used for experiments with hydrogen. About 80 years after that, the scientific hydrogen bag turned into a popular pastime: rubber balls were widely used in Europe during city holidays. Due to the gas that filled them, they could rise up - and this was very popular with the public, which had not yet been spoiled by either air flights or other miracles of technology. But these balloons were somewhat similar to their legendary predecessors: they used hydrogen (and, as you know, it is an explosive gas). But, nevertheless, everyone got used to hydrogen - fortunately, there were no special troubles from balloons with this gas until 1922. Then in the USA, at one of the city holidays, a joker blew up the decoration of the holiday for fun - that is, balloons. As a result of this explosion, an official was injured, and therefore law enforcement agencies reacted quite quickly. Fun that turned out to be dangerous enough
finally stopped by banning filling balloons with hydrogen. Nobody suffered from this decision - the place of hydrogen in the balloons was instantly taken by much safer helium. This new gas lifted the balloons just as well as hydrogen did. In 1931, Neil Tylotson released the first modern, latex balloon (polymer latex is obtained from aqueous dispersions of rubber). And since then, balloons have finally been able to change! Before that, they could only be round - and with the advent of latex, for the first time, it became possible to create long, narrow balls. This innovation immediately found application: holiday designers began to create compositions from balloons in the form of dogs, giraffes, airplanes, hats ... Neil Tylotson's company sold through the mail millions of balloon sets designed to create funny figures. The quality of balloons at that time was far from the same as now: when inflated, the balloons lost some of their brightness, they were fragile and quickly burst. Therefore, balloons slowly lost their popularity - the fact that they can fly in the air did not seem so wonderful and interesting in the twentieth century. Therefore, long before the end of the 20th century, balloons began to be bought up only for city and children's holidays. But the inventors did not forget about balloons, they worked to improve them. And the situation has changed. Now the industry produces such balloons that do not lose color when inflated - and in addition they have become much more durable and durable. Therefore, now balloons have again become very popular - designers are willing to use them when decorating various holidays, concerts, presentations. Weddings, birthdays, citywide celebrations, PR campaigns, shows… updated, bright balloons are everywhere in place. Here is such an interesting, long-standing history of a simple fun we have known since childhood.
Practical part
Experiment #1
Qualitative comparison of the densities of water - hot, cold and salty
If you investigate liquids that do not mix and do not enter into a chemical reaction, then it is enough just to pour them into one transparent vessel, for example, a test tube. The density can be judged by the arrangement of the layers: the lower the layer, the higher the density. Another thing is if the liquids are mixed, such as hot, cold and salt water.
We compare the behavior of balloons filled with hot, cold, and salted water in hot, cold, and salted water, respectively. As a result of the experiment, we can draw a conclusion about the densities of these liquids.
Equipment: three balls of different colors, a three-liter jar, cold, hot and salt water.
Experiment progress
Pour three portions of different water into balls - blue hot,
in green cold and in red salty water.
2. Pour hot water into the jar, put the balls there in turn (Appendix No. 1).
3. Pour cold water into the container, again place all the balls there in turn.
4.Pour salt water into the jar, observe the behavior of the balls.
Output:
1. If the density of liquids is different, then a liquid with a lower density floats above a liquid with a higher density, that is
hot water< холодной воды < соленой воды
2. The greater the density of the liquid, the greater its buoyancy force:
F A=Vg; since V and g are constant F Adepends on the size.
Experiment #2
Slimming and fattening ball. The fact that various bodies and gases expand from heat and contract from cold can be easily demonstrated using the example of a balloon. In frosty weather, take a balloon with you for a walk and inflate it tightly there. If you then bring this ball into a warm house, then it will most likely burst. This will happen due to the fact that from the heat the air inside the ball will expand dramatically and the rubber will not withstand the pressure.
Equipment: balloon, tape measure, refrigerator, hot water pot
Experiment progress
Task number 1 1. Inflate a balloon in a warm room.
2. Using a centimeter tape, we measured its circumference (we got 80.6 cm).
3. After that, put the ball in the refrigerator for 20-30 minutes.
4. Again measured its circumference. We found that the ball "lost" almost a centimeter (in our experiment, it became 79.7 cm). This happened due to the fact that the air inside the balloon was compressed and began to occupy a smaller volume.
Task number 2
1 With the help of a centimeter tape, we measured the circumference of the balloon (we got 80.6 cm).
2. Put the ball in a bowl and pour hot water from a jar over it.
3. We measure the new volume of the ball. We found that the ball "thickened" by almost a centimeter (in our experiment it became 82 cm). This happened due to the fact that the air inside the balloon expanded and began to occupy a larger volume.
Output: the air contained in the balloon contracts when cooled, and expands when heated, which proves the presence of thermal expansion. Gas pressure depends on temperature. When the temperature decreases, the air pressure in the ball decreases, i.e. the volume of the ball decreases. With an increase in temperature, the air pressure in the ball increases, which proves the dependence of the volume and pressure of gases on temperature.
Experiment #3
"Ball in the Bank"
Equipment: ball, three-liter jar, hot water.
The progress of the experiment.
1. Pour water into the balloon so that it does not pass into the neck of the jar.
2. Pour hot water into a jar, chat and pour it out. Leave the jar for 5 minutes.
3. We put a ball filled with water on a jar. We are waiting 20 minutes. The ball falls into the jar
Output: since the ball, filled with water and larger in diameter than the neck of the jar, fell inward, it means that there is a pressure difference: warm air inside the jar has a lower density than atmospheric air, the pressure inside is less; therefore, more atmospheric pressure encourages the ball to penetrate the can.
Experiment #4
"Air paradox"
This experience confuses many.
Equipment: two identical balloons, a tube 10-30 cm long and 15-20 mm in diameter (the ball should be tightly put on it). two balloons, differently inflated, plastic tube, stand.
The progress of the experiment.
1. Slightly and NOT EQUALLY inflate the balls.
2. We stretch the balls on opposite ends of the tube. To prevent the balls from being blown away, we twist their necks.
3. We open the necks for free communication of air between the balls.
observation. Air flows from one balloon to another. But ... a small balloon inflates a big one!
Explanation. Many believe that since the mass of air is greater in a larger balloon, then this balloon will deflate and inflate a small balloon. But such reasoning is erroneous. The reason for the observed phenomenon is the pressure inside the ball. (Recall communicating vessels - water flows not from the vessel where there is less water, but from the one where the pressure is greater.) In addition, everyone knows how difficult it is to start inflating a balloon, but when the “dead” point is overcome, then it inflates easily. Therefore, the elasticity of rubber plays an important role.
Output: The pressure of the gas inside the sphere is the greater, the smaller its radius.
Experiment #5
Ball - yoga
We are so accustomed to the fact that an inflated balloon, hitting the tip, bursts with noise,
that a ball on nails under the weight of a load is perceived by us as a supernatural phenomenon. Nevertheless, this is a fact.
Equipment: a board with nails, a balloon, a board, a weight, two tripods.
The progress of the experiment.
1. Put a balloon on a board with nails and press it with your hand from above.
2. We press on the ball with a previously measured load.
3. We observe the behavior of the ball.
Observations: the ball remains intact. And it's all about the footprint! The more nails, the more points of support for the body (i.e. more surface area on which the body rests). And all the force is distributed over all the nails in such a way that there is too little force on a single nail to pierce the ball.
Output: pressure is distributed evenly over the entire surface of the ball, and up to a certain point this pressure is harmless for the ball.
Experiment #6
Electrostatic field indicator
Information. It is convenient to study electrostatic fields with the help of indicators that allow one to estimate the direction and magnitude of the Coulomb force at each point of the field. The simplest point indicator is a light conducting body suspended on a thread. Previously, it was recommended to use the core of an elder branch to make a light ball. At present, it is advisable to replace elderberry with foam plastic. Other solutions to the problem are also possible.
The task. Design and manufacture the simplest indicator of the electrostatic field. Experimentally determine its sensitivity.
The progress of the experiment.
1. From a piece of rubber from a children's balloon we blow out a rubber ball 1 with a diameter of 1-2 cm. Tie the ball to a silk thread 2 , which is reinforced to a rubber stopper.
2. We rub the surface of the ball to a characteristic metallic sheen with graphite powder from the lead of a soft simple pencil.
3. The ball was loaded from an ebonite stick worn with fur.
4. Enter the indicator in the field of a spherical charge and evaluate the sensitivity of the indicator by the magnitude of the acting force.
Output: a small rubber ball covered with a conductor is a point indicator of the electric field.
Experiment #7
Ball and boat
Equipment: paper boat, metal plastic cover,
vessel with water.
The progress of the experiment.
1. We make a paper boat and put it on the water.
2. We electrify the ball and bring it to the boat.
observation. The ship will follow the ball.
3. We lower the metal cover into the water.
4. We electrify the ball and bring it to the lid without touching it.
observation. The metal cover floats towards the ball.
5. We lower the plastic cover into the water.
6. We electrify the ball and bring it to the lid without touching it.
observation. The heavy lid floats behind the ball.
Output: In the electric field of the ball, paper and plastic are polarized and attracted to the ball. A charge is also induced in the metal cover. Since the friction force on the water is negligible, the boats easily set in motion.
Experiment #8
jumpers
Equipment: balloon, finely cut metal foil, cardboard sheet.
The progress of the experiment.
1. Pour finely chopped metal foil onto a sheet of cardboard.
2. We electrify the ball and bring it to the foil, but do not touch it.
observation. Sequins behave like living jumping grasshoppers. They jump, touch the ball and immediately fly off to the side.
Output: Metallic sequins are electrified in the field of the ball, but at the same time remain neutral. The sequins are attracted to the ball, bounce, charge when touched and bounce as if they were charged with the same name.
Experiment #9
Air kiss according to Bernoulli's law
Equipment: 2 balloons, 2 threads 1 m long.
The progress of the experiment.
1. We inflate the balls to the same size and tie a thread to each.
2. We take the balls by the thread with the right and left hands so that they hang at the same level at some distance from each other.
3. Without touching the balls with your hands, try to connect them.
Explanation. From Bernoulli's law it follows that the pressure in the air stream is lower than atmospheric pressure. The force of atmospheric pressure from the sides will bring the balls together.
Experiment #10
Thermal strength test
Equipment: ball and candle
The progress of the experiment.
Pour water into the ball and bring the ball of water into the flame of the candle.
observation. The rubber is just smoky.
Explanation. The temperature of the shell, as long as there is water in it, will not rise above 100 °C, i.e. will not reach the combustion temperature of the rubber.
Experiment #11
How do the lungs work?
Equipment: plastic bottle, balloon number 1, balloon number 2 (I used a plastic bag instead), scotch tape.
The progress of the experiment.
1. Cut off the bottom of the plastic bottle
2. We place the balloon inside the bottle and pull it over the neck.
3. Tighten the cut off part with a fly from another balloon (or a plastic bag) and secure with tape.
4. We pull the film - the ball is inflated, we press on the film - the ball is deflated.
Explanation. The volume of air inside the bottle is isolated. When the film is pulled back, this volume increases, the pressure decreases and becomes less than atmospheric. The balloon inside the bottle is inflated with atmospheric air. When pressing on the film, the volume of air in the bottle decreases, the pressure becomes greater than atmospheric pressure, and the balloon is deflated. Our lungs do the same.
Experiment #12
Balloon as a jet engine
Equipment: balloon, straw, stationery gum, adhesive tape, car.
The progress of the experiment.
1. The balloon must be fixed at one end of the tube with a rubber band.
2. The second end of the tube must be fixed on the body of the machine with adhesive tape so that it is possible to inflate the ball through the tube.
3. The model is ready, you can run! To do this, you need to inflate the balloon through the tube, pinch the opening of the tube with your finger and put the machine on the floor. As soon as you open the hole, the air from the balloon will fly out and push the car. -12-
Explanation. This visual model demonstrates how jet engines work. The principle of its operation is that the jet of air escaping from the balloon, after it has been inflated and released, pushes the machine in the opposite direction.
3.Conclusion
On balloons, you can study the laws of pressure of bodies and gases, thermal expansion (compression), thermal conductivity, density of liquids and gases, Archimedes' law; electrification of bodies, it is even possible to construct instruments for measuring and studying physical processes.
The experiments carried out in this research work prove that the ball is an excellent tool for studying physical phenomena and laws. You can use this work at school in the classroom when studying the sections "Initial information about the structure of matter", "Jet propulsion", "Pressure of solids, liquids and gases", "Thermal and electrical phenomena". The collected historical material is applicable in the classroom in physics and extracurricular activities.
A computer presentation created on the basis of the practical part will help schoolchildren to quickly understand the essence of the physical phenomena being studied, and will cause a great desire to conduct experiments using the simplest equipment.
Obviously, our work contributes to the formation of genuine interest in the study of physics.
4.Literature
www.demaholding.ru
[Electronic resource]. Access mode: www.genon.ru
[Electronic resource]. Access mode: www.brav-o.ru
[Electronic resource]. Access mode: www.vashprazdnik.com
[Electronic resource]. Access mode: www.aerostat.biz
[Electronic resource]. Access mode: www.sims.ru
Turkina G. Physics on balloons. // Physics. 2008. No. 16.
The ball is at rest, since the action of these forces is compensated.
