Review Questions

1. A skater moving at 3 m/s falls. How far does she slide before coming to a stop?

2. A block of mass 2 kg slides down a frictionless slope and compresses a spring at the bottom by 3 cm. What was the block's decrease in height? Do you need to know the angle of the slope? What is the future of this block?

3. From a hook hangs a spring with spring constant 2000 N/m. From this spring hangs a mass of 1 kg. From that mass hangs a spring with spring constant 1000 N/m. From that spring hangs a mass of 3 kg. By how much is each spring stretched? Assume both springs have negligible mass.

4. A car's parking brake fails (happens a lot in this course) and it rolls down a hill, where it hits a car whose parking brake wasn't applied in the first place. The first car bounces back, and the second car moves forward and starts up another hill. What can you tell me about these two cars' masses? Does the second car roll up the hill to the height at which the first car started? or lower, or higher, or can't you be sure? What if the roles of these two cars were reversed?

5. A bullet is fired at 400 m/s, hits a block of wood, and comes to rest after travelling 3 cm into the wood. An identical bullet is fired at the same piece of wood (but not at exactly the same spot) at 350 m/s. How far into the wood does this second bullet travel?  If the bullet has a mass of 10 g, what force does the wood exert on it?

6. We have a seesaw, consisting pretty much of a 4 m long board of mass 25 kg, pivoted on a pipe at the center of the board. Two children, one of mass 45 kg and the other of mass 30 kg, want to play on this seesaw. The idea is to be pretty balanced, so you don't end up with one child on the ground and the other in the air all the time. Where should each child sit?

7. It sure was hard to throw a ball to someone on the other side of the merry-go-round, wasn't it? Devise a strategy for tossing the ball to someone on the other side of the merry-go-round. Draw the path the ball follows relative to the ground, and the path it follows relative to the merry-go-round.

8. Estimate the force exerted by the swing on Will when he was at the lowest point of the arc.