Honors Physics

# Questions - Week 20

1. What is the Second Law of Thermodynamics?
2. When most people use the word 'energy' they are not using it as a physicist would use it. I suggested four different uses of the word energy. What were they?
3. Energy transfer is one of the most common happenings in nature. What is it that transfers energy?
4. If you lift a book off the ground, are you doing positive or negative work? Is the earth doing positive or negative work?
5. A rope pulls on a 20.0 kg box at an angle 37.0° above the horizontal. If the tension in the rope is 160 N, how much work is done as the box moves 10.0 m along a horizontal surface?
6. A 1200 kg car is moving at 23 m/s. How much work is required to stop the car?
7. A 4.0 kg rock is sliding along a horizontal, frictionless surface at 5.0 m/s. How much force would be needed to stop the rock over a distance of 1.2 m?
8. Pull a 35 kg box 2.5 m across the floor using a 240 N force, 35° above the horizontal. If the kinetic frictional coefficient is 0.40 what is the net work done on the box?
9. A common unit on electric bills is the kiloWatt-hour. Is this a unit of work, energy or power?
10. The change in kinetic energy of an object is equal to...
11. A 3.5 kg rock is at rest on the ground. Pick up the rock and place it on a table 1.0 m high. How much work was done on the rock?
12. A rope exerts an 18.0 N force while lowering a 20.0 kg crate down a slope. The force is parallel to the slope, and the angle of the slope is 20.0° above the horizontal. If a 24.0 N frictional force opposes the motion of the crate, find its speed after sliding 10.0 m down the slope.
13. What is a conservative force?