Physics notes: Work, Energy, Power

1. A sumo wrestler of mass 200kg pushes a wall with a force of 1500N. The wall crumbles. What is the work done by the sumo wrestler?

2. A ball falls from a height of 10m. At every bounce, 50% of the ball’s energy is converted into heat and sound energy. What is the height that the ball bounces to after the 3rd bounce? Neglect air resistance.

3. A block is pushed at a constant velocity of 4m/s. The work done in moving it 5m is 100J. What is the frictional force acting on it?

4. A force of 100N is applied to a stationary block. It moves, experiencing an opposing frictional force of 20N. It covers a distance of 4m. Given that the force was exerted by a machine of power 100W, how long did the block take to move the entire 4m?

5. In the previous question, what was the amount of energy used to overcome friction?

6. A mass of water takes 0.5 hours to boil. How much heat energy is needed to boil the water using a 2000W kettle?

7. A block of mass 50kg is dropped from a building 500m tall and makes a dent in the ground that is 5cm deep. What is the speed at which it hits the ground?

8. A ball with an initial velocity of 5m/s rolls across a surface and eventually comes to a rest after 10m. It experiences 6N of frictional force throughout its motion. What is the weight of the stone?

9. The efficiency of a car’s 2000kW engine is 70%. It is used for 10 minutes to drive at a constant velocity against a frictional force of 100kN. How far does it travel?

10. What is power?

1. A sumo wrestler of mass 200kg pushes a wall with a force of 1500N. The wall crumbles. What is the work done by the sumo wrestler?

2. A ball falls from a height of 10m. At every bounce, 50% of the ball’s energy is converted into heat and sound energy. What is the height that the ball bounces to after the 3rd bounce? Neglect air resistance.

3. A block is pushed at a constant velocity of 4m/s. The work done in moving it 5m is 100J. What is the frictional force acting on it?

4. A force of 100N is applied to a stationary block. It moves, experiencing an opposing frictional force of 20N. It covers a distance of 4m. Given that the force was exerted by a machine of power 100W, how long did the block take to move the entire 4m?

5. In the previous question, what was the amount of energy used to overcome friction?

6. A mass of water takes 0.5 hours to boil. How much heat energy is needed to boil the water using a 2000W kettle?

7. A block of mass 50kg is dropped from a building 500m tall and makes a dent in the ground that is 5cm deep. What is the speed at which it hits the ground?

8. A ball with an initial velocity of 5m/s rolls across a surface and eventually comes to a rest after 10m. It experiences 6N of frictional force throughout its motion. What is the weight of the stone?

9. The efficiency of a car’s 2000kW engine is 70%. It is used for 10 minutes to drive at a constant velocity against a frictional force of 100kN. How far does it travel?

10. What is power?