1. a student drops a rock from a bridge to the water 12 m below. a) how many seconds does it take the rock to hit the water? b) how fast is the rock moving when it hits the water?
2. a weather balloon is floating at a certain height above the earth when it releases a heavy pack of instruments. a) if the pack hits the ground with a speed of 73 m/s, how far up is the balloon? b) how long does it take the instrument pack to reach the ground?
3. an engineer must design a runway that allows planes to reach a ground speed of 61 m/s before they can take off. if the planes accelerate at 2.4 m/s2 , what must be the minimum length of the runway?
4. a rock is thrown straight down, not dropped, from the roof of a building that is 61 m above the ground. if it takes 3.1 s to reach the ground, with what speed was it thrown? © 2004, gpb 3-21
5. a baseball is hit straight up into the air with a speed of 33 m/s. a) how high does it go? b) how long is it in the air?
6. an astronaut drops a feather from 1.25 m above the surface of the moon. the acceleration due to gravity on the moon is 1.62 m/s2 . a) how long does it take the feather to hit the ground? b) how long would it take a hammer to fall the same distance?
7. a tennis ball is dropped 1.2 m above the ground. with what velocity does it hit the ground (before the ground stops it)?