Consequently, work is equal to energy that has changed from one type to another. Test "Work

1. In rectilinear motion, the speed of a material point is directed: 1) to the same direction as the movement; 2) against the direction of movement; 4) regardless of the direction of movement;
2. A physical quantity equal to the ratio of the displacement of a material point to a physically small period of time during which this movement occurred is called 1) the average speed of the uneven movement of a material point; 2) the instantaneous speed of a material point; 3) the speed of uniform movement of a material point.
3. In which case is the acceleration modulus greater? 1) the body moves at a high constant speed; 2) the body is rapidly gaining or losing speed; 3) the body is slowly gaining or losing speed.
4. Newton's third law describes: 1) the action of one body on another; 2) the action of one material point on another; 3) the interaction of two material points.
5. The locomotive is coupled to the carriage. The force with which the locomotive acts on the car is equal to the forces that impede the movement of the car. Other forces do not affect the movement of the carriage. Consider the frame of reference connected to the Earth as inertial. In this case: 1) the carriage can only be at rest; 2) the car can only move at a constant speed; 3) the carriage is moving at a constant speed or is at rest; 4) the car is moving with acceleration.
6. An apple weighing 0.3 kg falls from the tree. Choose the correct statement 1) the apple acts on the Earth with a force of 3H, and the Earth does not act on the apple; 2) The Earth acts on the apple with a force of 3H, and the apple does not act on the Earth; 3) the apple and the Earth do not act on each other; 4) the apple and the Earth act on each other with a force of 3 N.
7. Under the action of a force of 8N, the body moves with an acceleration of 4m / s2. What is its mass equal to? 1) 32 kg; 2) 0.5kg; 3) 2 kg; 4) 20kg.
8. With dry friction, the maximum force of static friction is: 1) greater than the force of sliding friction; 2) less force of sliding friction; 3) is equal to the sliding friction force.
9. The force of elasticity is directed: 1) against the displacement of particles during deformation; 2) in the direction of particle displacement during deformation; 3) nothing can be said about its direction.
10. How do the mass and weight of a body change when it moves from the equator to the pole of the Earth? 1) the mass and weight of the body do not change; 2) body weight does not change, weight increases; 3) body weight does not change, weight decreases; 4) body weight and weight decrease.
11. After turning off the rocket engines, the spacecraft moves vertically upward, reaches the top point of the trajectory and then moves downward. On what part of the trajectory in the ship is the state of weightlessness observed? Air resistance is negligible 1) only during upward movement; 2) only during downward movement; 3) only at the moment of reaching the top point of the trajectory; 4) during the entire flight with inoperative engines.
12. An astronaut on Earth is attracted to it with a force of 700N. With what approximately force will it be attracted to Mars, being on its surface, if the radius of Mars is 2 times, and the mass is 10 times less than that of the Earth? 1) 70N; 2) 140 N; 3) 210 N; 4) 280H.
Part 2
1) The body is thrown at an angle to the horizon with an initial speed of 10 m / s. What is the speed of the body at the moment when it was at a height of 3 m? Determine the force of gravity acting on a body weighing 12 kg, lifted above the Earth at a distance equal to a third of the Earth's radius.
2) What work needs to be done to lift a 30 kg load to a height of 10 m with an acceleration of 0.5 m / s2?

Option 1

1.A body weighing 1kg rises to a height of 5m. What is the work of gravity when lifting the body.

A. 50J B.150J C. 250J.

2. Determine the minimum power that the lift motor must have in order to lift a 0.05t load to a height of 10m in 5s.

A.2kW B.1kW B.3kW.

3. When cycling on a horizontal road at a speed of 9 km / h, a power of 30W is developed. Find the driving force.

A.12N B. 24N V. 40N.

4. A body weighing 2kg has a potential energy of 10J. To what height above the earth is the body lifted if the zero of the potential energy is located on the earth's surface?

A.1m B. 0.5m C. 2m

5. What is the potential energy of the striking part of a 300 kg pile hammer raised to a height of 1.5 m?

A. 4500J B. 5000J C. 6000J.

6. What is the maximum potential energy of a bullet ejected from a gun, if its velocity at exit is 600 m / s, and its mass is 9g?

A. 460J B.1620J W. 2500J.

7. With what speed was a stone thrown vertically upwards, if it rose to a height of 5m?

A.10m / s B.5m / s V. 2m / s.

8. An airplane with a mass of 2 tons is moving in a horizontal direction at a speed of 50 m / s. Being at an altitude of 420m, it descends with the engine off and reaches the airfield track with a speed of 30m / s. What is the work of the air resistance force during gliding flight?

A. -10MJ B.10MJ V. -20MJ.

9. Two carts move towards each other at a speed of 4m / s each. After the collision, the second bogie got a speed in the direction of movement of the first bogie equal to 6 m / s, and the first stopped. Calculate the mass of the first trolley if the mass of the second is 2kg.

10. A stone with a mass of 20 g, released vertically upwards from a slingshot, the rubber band of which was stretched by 20 cm, rose to a height of 40 cm. Find the stiffness of the harness.

Option 2

1.A body weighing 2kg is raised to a height of 2m. What is the work of gravity when lifting the body

A. 40J B. 80J C. 60J.

2. Calculate the power of the pump that delivers 1200kg of water every minute to a height of 20m.

A.4kW B.10kW V. 20kW.

3. The thrust force of a supersonic aircraft at a flight speed of 2340 km / h is 220 kN. What is the power of the aircraft engines in this flight mode?

A. 143 MW B. 150 MW C. 43 MW.

4. A body raised above the ground to a height of 2m has a potential energy of 40J. What is the mass of this body if the zero of the potential energy is located on the surface of the earth?

A. 2kg B. 4kg B. 5kg

5. What is the change in the potential energy of a 200kg load that fell to the ground from a height of 2m?

A. -4500J B. -4000J C. 4000J.

6. What is the kinetic energy of a body with a mass of 3 kg, moving at a speed of 4 m / s?

A. 20J B. 30J C. 24J.

7. The ball is thrown vertically upward at a speed of 10m / s. Determine the maximum height the ball will climb.

A.10m B. 5m C. 20m

8. A stone thrown vertically upward at a speed of 20 m / s fell to the ground at a speed of 10 m / s. Stone weight200g. What is the work of the air resistance force?

A. -30J B. 30J W. -40J.

9. Two balls are moving towards each other at the same speed. The mass of the first ball is 1kg. What mass should the second ball have for the first ball to stop after the collision, and the second to roll back at the same speed?

10. When preparing a toy pistol for a shot, the spring with a stiffness of 800n / m was compressed by 5cm. What velocity does a 20g bullet acquire when fired horizontally?

Option 3

1. A ball of mass m moves with a speed v and collides with the same motionless ball. Assuming the impact is absolutely elastic, determine the velocity of the balls after the impact.

A. v 1 \u003d 0; v 2 \u003d v B. v 1 \u003d 0; v 2 \u003d 0 B. v 1 \u003d v; v 2 \u003d v.

2. What is the modulus of change in the impulse of a body of mass m moving with a velocity v, if after collision with a wall the body began to move in the opposite direction with the same modulus of velocity?

A. 0 B. mv B. 2mv.

3. A material point weighing 1 kg moves uniformly around a circle at a speed of 10m м s. Determine the change in impulse over half a period.

A. 0 kg m ∕ s B. 14 kg ∙ m ∕ s B. 20 kg m ∕ s.

4. How many times is the potential energy accumulated by the spring when compressed from the equilibrium position by 2 cm less than when the same spring is compressed by 4 cm?

A. 2 times B. 8 times C. 4 times.

5. How will the kinetic energy of a body change when its velocity doubles?

A. Increase 4 times B. Decrease 4 times C. Increase 2 times.

6. A bullet is fired from a spring pistol located 2m above the ground. First time vertically upward, second time horizontally. In what case will the bullet velocity be greatest when approaching the earth's surface? Neglect air resistance. The speed of the bullet from the pistol is considered the same in all cases.

A. In the first B. In the second B. In all cases, the final velocity of the bullet will be the same in absolute value.

7. The figure shows the trajectory of a body thrown at an angle to the horizon (neglect air resistance). The kinetic energy is equal to the potential at the point

A. 2 B. 3 C. 4

D. At all points is equal.

8. A proton moving at a speed of 2 · 10 4 m / s collided with a stationary nucleus of a helium atom. Calculate the velocity of the nucleus of a helium atom after impact if the velocity of the proton has decreased to 0.8 · 10 4 m / s. The mass of the helium nucleus is 4 times the mass of the proton.

9. When preparing a toy pistol for a shot, the spring with a stiffness of 800 N / m was compressed by 5 cm. What speed does a bullet weighing 20 g acquire when fired horizontally.

10. Calculate the average soil resistance force if a body with a mass of 2 kg, thrown from a height of 250 m vertically downward with an initial velocity of 20 m / s, plunged into the ground to a depth of 1.5 m.

This test contains 23 options for assignments of different levels on the topic "Work, power, simple mechanisms" for the 9th grade (according to the physics textbook for the 9th grade by the authors Shakhmaev N.M., Bunchuk A.V.). Each option contains a different number of quality and design problems of different levels. Knowing the individual characteristics of the student, it is possible in this work to select tasks that are feasible for each child. I would be glad if this publication is useful to someone. Download, recycle. Good luck!

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9kl. (according to Shakhmaev).

Examination work No. 3.

Work, power, simple mechanisms.

Option # 1

A body weighing 1 kg with a force of 20 N rises to a height of 5 m. What is the work of this force?
Give a detailed answer: is it possible to move a sailboat by directing a stream of air from a powerful fan on the boat to the sails?
Determine the minimum power that the lift motor must have to lift a 50kg load to a height of 10m in 5s. Find efficiency
What work is done by the force of gravity acting on a raindrop weighing 20 g when it falls from a height of 1 km?

Option number 2

A body weighing 1kg rises to a height of 5m. What is the work of gravity?
Give a detailed answer: a stone and a tennis ball are hit with a stick. Why does the ball fly farther than a stone, other things being equal?
Calculate the power of the pump that delivers 1200kg of water every minute to a height of 20m.
A stone weighing 400 g was thrown vertically upward at a speed of 20 m / s. What are the kinetic and potential energies of a stone at a height of 15m?
A piano weighing 300 kg was fed into a sixth floor window, located 16 m above the sidewalk, using a lifting device in 50 seconds. Determine the work, power, efficiency.

Option number 3

The weightlifter, lifting the barbell, performs work of 5 kJ in 2 s. Determine the power and efficiency.
What weight can the lifting machine lift to a height of 30 m in 4 minutes if the engine power is 5 kW?

Option number 4

Kot Matroskin and Sharik towed Uncle Fedor's car to Prostokvashino for 1 hour, acting with a force of 120 N. Distance to Prostokvashino is 1 km. Determine the work, efficiency and power
What is the power developed by a tractor at a speed of 9.65 km / h and a pulling force of 15 kN?
What work is done with a uniform lifting of an iron beam with a volume of 0.1 m3 to a height of 15 m?

Option number 5

1. A boy weighing 40 kg climbed in 30 seconds to the second floor of the house, located at a height of 8 m. Determine the work and power
What kind of work does an excavator do when lifting 14 m of soil with a bucket?3 to a height of 5 m? Soil density 1400 kg / m3 .
The climber climbed in the mountains to a height of 2 km. Determine the mechanical work performed by the climber when ascending if his weight with equipment is 85 kg.
How much weight can the lifting machine lift to a height of 30 m in 4 minutes, if the engine power is 5 kW? Find efficiency
A force of 4 N and 20 N acts at the ends of the lever, the length of the lever is 1.5 m. Where is the fulcrum if the lever is in balance?

Option number 6.

A person, walking for 2 hours, makes 10,000 steps (40 J work is done in one step). Determine the work, power and efficiency.
What work does the force of gravity, acting on a raindrop weighing 20 g, do when it falls from a height of 2 km?
The thrust force of a supersonic aircraft at a flight speed of 2340 km / h is 220 kN. Find the power of the aircraft engines in this flight mode.
Weights of 4 and 24 kg are suspended from the lever. The distance from the fulcrum to the larger load is 4 cm. Determine the length of the arm if the arm is in balance.

Option number 7

Baba Yaga stupa (weight 70 kg) flies 120 km in 1 hour. Determine the work, power
The crane lifted a 5 t load to a height of 10 m in 45 s. Determine the crane motor power and efficiency
The locomotive develops a traction force of 400 kN at a speed of 54 km / h. What work is done to move the train within 1 minute?
A force of 4 N and 20 N acts at the ends of the lever, the length of the lever is 1.5 m. Where is the fulcrum if the lever is in balance?

Option number 8

Carlson lifts the Kid weighing 30 kg to the roof of a house 20 m high in 10 seconds. Determine Carlson's Job and Power
The spring of a toy pistol, compressed by 3 cm, pushes the ball out in 1 s, acting on it with a force of 10N. Determine work, power and efficiency.
The Zhiguli car travels 100 m in 6.25 s, developing a thrust of 3 kN. Determine work and power
4. The atomic icebreaker, developing a power of 32400 kW, covered 20 km in 5 hours. Determine the average force of resistance to the movement of the icebreaker.
Weights of 4 and 24 kg are suspended from the lever. The distance from the fulcrum to the larger load is 4 cm. Determine the length of the arm if the arm is in balance.

Option number 9.

The crane lifts a concrete slab weighing 5 tons to a height of 9 m for 1 minute. Determine the work, power and efficiency.
The boy evenly lifted the bucket of water from the well once in 20 seconds, and the other in 30 seconds. Was the same work done in these cases? What can you say about the power when performing these works?
The cyclist performed 800 J in 10 seconds. What is the power of the cyclist?
How much weight can the lifting machine lift to a height of 30 m in 4 minutes, if the engine power is 5 kW?
A force of 4 N and 20 N acts at the ends of the lever, the length of the lever is 1.5 m. Where is the fulcrum if the lever is in balance?

Option number 10

How long will it take to pump out water weighing 2 tons, if the pump power is 1.5 kW? Water rise height 20 m. Find efficiency
Academician B. S. Jacobi invented the electric motor in 1834. In the first version, the electric motor lifted a 5 kg load to a height of 60 cm in 2 s. Determine the engine power.
What is the power developed by a tractor at a speed of 9 km / h and a pulling force of 10 kN?
The atomic icebreaker, developing a power of 32400 kW, covered 20 km in ice in 5 hours. Determine the average force of resistance to the icebreaker's movement.
Weights of 4 and 24 kg are suspended from the lever. The distance from the fulcrum to the larger load is 4 cm. Determine the length of the arm if the arm is in balance.

Option number 11

To what height should a weight of 100 N be lifted to do the work

200 J?

Determine the work done when lifting a 4 N load to a height of 4 m
Determine the work done by a 400 W motor in 30 seconds. What is the efficiency?
How much weight can the lifting machine lift to a height of 30 m in 4 minutes, if the engine power is 5 kW?
A force of 4 N and 20 N acts at the ends of the lever, the length of the lever is 1.5 m. Where is the fulcrum if the lever is in balance?

Option number 12

How long does a 200 W electric motor have to run to do 2500 J?
When cycling on a horizontal road at a speed of 9 km / h, a power of 30 watts is generated. Find the driving force.
Calculate the power of the pump, which delivers 1200 kg of water every minute to a height of 20 m

The atomic icebreaker, developing a power of 32,400 kW, covered 20 km in ice in 5 hours.
Determine the average force of resistance to the movement of the icebreaker and efficiency. icebreaker
Weights of 4 and 24 kg are suspended from the lever. The distance from the fulcrum to the larger load is 4 cm. Determine the length of the lever if the lever is in

balance.

Option number 13

The crane lifts the load at a constant speed of 5.0 m / s. Crane power 1.5 kW. What

can the load be lifted by this crane?

When preparing a toy pistol for a shot, a spring with a stiffness of 800 N / m

squeezed by 5 cm. What velocity will a 20 g bullet acquire when fired horizontally?

A force of 4 N and 20 N acts at the ends of the lever, the length of the lever is 1.5 m. Where is the fulcrum if the lever is in balance?

Option number 14

A ball weighing 100 g freely fell onto a horizontal platform, having a velocity of 10 m / s at the moment of impact. Find the drop height, neglect friction.
1.8 ∙ 10 falls from a dam with a height of 20 m4 tons of water. What kind of work is being done?
Determine the potential energy of a spring with a stiffness of 1.0 kN / m if it is known that the compression of the spring is 30 mm.
Carlson lifts the Kid weighing 20 kg to the roof of a house 20 m high in 10 seconds. Determine Carlson's Job and Power

Option number 15

Determine the net engine power of a motorcycle if at a speed of 108 km / h its thrust is 350 N.
What work is done when lifting from the ground the materials needed to build a column 20 m high with a cross-sectional area of \u200b\u200b1.2 m2 ? The density of the material is 2.6 ∙ 103 kg / m 3.
Determine how fast you need to throw the ball down from a height of 3 m so that it bounces to a height of 8 m.
A force of 4 N and 20 N acts at the ends of the lever, the length of the lever is 2 m. Where is the fulcrum if the lever is in balance?

Option number 16

With an aircraft speed of 900 km / h, its four engines develop a net power of 30 MW. Find the thrust of each engine in this flight mode.
Determine the work to be done when digging a well with a diameter of 1.0 m and a depth of 10 m, if the soil density is 1.8 ∙ 103 kg / m 3 ... Consider that the soil is scattered in a thin layer over the surface of the earth.

3. A stone weighing 20 g, released vertically upward from a slingshot, a rubber band that was stretched by 10 cm, rose to a height of 40 cm. Find the stiffness of the spring.

4. Determine the minimum power that the hoist motor must have to lift a 50kg load to a height of 10m in 5s. Find efficiency

Option number 17

The crane evenly lifts a 500kg load to a height of 10m in 50s. Determine the efficiency of the crane if its motor power is 1.5 kW.
The spring, compressed to 30cm, is fully extended. What work did the elastic force do if the spring rate is 100N / m?
Determine the work of the friction force if a body with a mass of 2 kg changes its speed from 4 to 3 m / s?
A 250g ball is thrown vertically upward at a speed of 20m / s. What is its kinetic energy at a height of 10m.

Option number 18

The box is pulled evenly along a horizontal surface by a rope forming an angle of 60 ° with the horizon. The force applied to the rope is 25N. What kind of work is done when the box is moved at a distance of 4m?
At an altitude of 15m above the Earth's surface, the building block has a potential energy of 1500 kJ. What is its mass equal to?
The spring has a stiffness of 2500 N / m. What energy does the spring have when compressed by 10cm?
An arrow with a mass of 20 g is fired from the bow vertically upwards at a speed of 20 m / s. Determine its kinetic energy at a height of 15m.
The atomic icebreaker, developing a power of 32400 kW, covered 20 km in ice in 5 hours. Determine the average resistance to the icebreaker movement and efficiency. icebreaker

Option number 19

A body weighing 1kg with a force of 20N rises to a height of 5m. What is the work of this force?
The ball, lowered under water to a depth of 30 cm, is pushed out with a force of 5N. Define the job.
The spring is compressed by 4 cm. The spring rate is 100 kN / m. What kind of work will she do?
Useful work 20kn, all consumed energy is equal to 40,000 N. Find efficiency
Name the transitions of energy when falling

Option number 20

Weights of 4 and 24 kg are suspended from the lever. The distance from the fulcrum to the larger weight is 4 cm. Determine the distance to the second weight if the arm is in balance.
The spring is compressed by 50 cm. The spring rate is 10 kN / m. What is the energy of the spring?
Determine the work of gravity when a body weighing 4 kg falls from a height of 200 cm.
What is meant by the energy of the body? List the types of energy.

Option number 21

The climber climbed in the mountains to a height of 1.5 km. Determine the mechanical work performed by the climber during the ascent if his weight with equipment is 100 kg.
What is the payoff for the movable block?
Write down formulas of different types of energies
Where and for what purpose is the gate used?

Option number 22

2. What is the inclined plane for?

3. The spring, compressed by 10cm, is fully extended. What work did the elastic force do if the spring rate is 1kN / m?

4. At a height of 10m above the Earth's surface, the building block has a potential energy of 150 kJ. What is its mass equal to?

Option number 23

1. What is the payoff for the movable block?

2. A nuclear icebreaker, developing a power of 32400 kW, covered 20 km in ice in 5 hours. Determine the average force of resistance to the movement of the icebreaker.

3. Weights of 4 and 24 kg are suspended from the lever. The distance from the fulcrum to the larger load is 4 cm. Determine the length of the arm if the arm is in balance.

4. Carlson lifts the Kid weighing 30 kg to the roof of a house 20 m high in 10 seconds. Determine Carlson's Job and Power

Option number 24

The crane lifts the load at a constant speed of 5.0 m / s. Crane power 1.5 kW. What load can this crane lift?
Determine at what height is the kinetic energy of a ball thrown vertically upward at a speed of 23 m / s equal to its potential?
When preparing a toy pistol for a shot, the spring with a stiffness of 800 N / m was compressed by 5 cm. What velocity will a 20 g bullet acquire when fired in a horizontal direction?
Forces 5 and 6 N act on the lever from below at angles of 45 and 30 degrees at a distance of 20 and 40 cm, respectively, from the support located in the middle of the lever. Find the force that can be used to balance the system by applying it vertically at a distance of 10 cm from the axis of rotation.