General Physics
Problem Set 4
Work, Kinetic Energy, Conservation of Energy and Power
1. A 105 kg bobsled is pushed from rest along a horizontal surface by four athletes.
After the bobsled has been pushed a distance of 6.5 m, its speed is 8.0 m/s. What
is the magnitude of the net force on the bobsled?
2. A 25.0 kg crate initially sliding at 3.50 m/s on a rough surface is brought to rest
by 5.0 N of friction. What distance does the box slide?
3. A space ship of mass 7.00×104 kg is traveling at a speed 2.50 × 104 m/s in outer
space. As the engine exerts a constant force of 4.50 × 105 N, the ship moves a
distance of 1.50 × 106 m in the direction of the force of the engine. Determine the
final speed of the ship.
4. A car experiences a net force of 63.5 N while it is speeding up from 25.0 m/s to
45.0 m/s over a distance of 675m. What was the car’s mass?
5. Donald Duck is at the top of Mt. Gushmore, at an elevation of 28.0 meters.
Donald has a mass of 54.7 kg. He goes down the waterslide to the bottom of Mt.
Gushmore. How fast is Donald going when he is at the bottom of the slide?
6. A pendulum bob is released from some initial height such that the speed of the
bob at the bottom of its swing is 2.2 m/s. What is the initial height of the bob?
7. Starting from rest, a 22.5 kg child goes down a 3.25 m tall slide. How fast is she
going when she is one fourth the way down the slide?
8. A 234 kg curtain must be raised 6.3 m in no more than 4.5 seconds. How much
power is needed to do this?
9. A rain cloud contains 3.55 x 107 kg of water vapor. How long would it take for a
3.50 x 103 W pump to raise the same amount of water to the cloud’s altitude, 1.75
km?
10. A ship generates 4.7 x 107 W of power. How much work can this ship do in 1.75
hour?