Physics Name ______________________

Period ________________ Date _______________________

Ch 12: Work Power GPE KE Practice Problems # 1

1. Calculate the work done as a 100-N force pushes a crate 5 m along a factory floor?

2. A person lifts a 50-N box vertically 3 m up a ladder?

a) What is the amount of work done by the person on the box?

b) What is the gravitational potential energy (GPE) of a 50-N box when it is raised 3 m?

c) Is the GPE of the box the same, less or more than the work done by the person on the box?

3. Calculate the power expended by the person who carries the 50-N box 3 m high in 3 s.

4. Calculate the kinetic energy of a 10-kg cart traveling at 4 m/s.

5. A 35-kg cheetah runs at 20 m/s (46 mph). What is its kinetic energy?

6. A 150-kg roller coaster car is 40 meter high from the bottom of the ride and traveling at 2.0 m/s.

a) What is the car total mechanical energy (ME = GPE + KE) at that height?

b) At the bottom of the ride (height h = 0 m), all the car’s mechanical energy is converted to kinetic

energy KE. What is the car speed at the bottom of the ride? (Remember that the car mass is 150-kg).

7. A rock in free fall has a kinetic energy of 5.0 J and a gravitational potential energy of 10.0 J (relative to

the floor).

a) What is the total mechanical energy ME of the rock?

b) As it continues to fall, its GPE changes to 3.0 J. What is its kinetic energy KE at this point?

c) If the mass of the rock is 0.50 kg, what is its speed at this point?

8. A 50-gk pole vault athlete wishes to clear a 4-m high bar.

a) What would his GPE be at the top of the 4-m high jump?

b) Assuming that when he is running at the ground level, all of his kinetic energy is converted into

gravitational potential energy. How fast must he run?