1. A runner with a mass of 76 kg accelerates from 0 to 9.4 m/s in 2.8 s. a) What
ID: 1992591 • Letter: 1
Question
1. A runner with a mass of 76 kg accelerates from 0 to 9.4 m/s in 2.8 s.a) What is the change in momentum of the runner?
b) How much force was used to accelerate the runner?
c) What impulse is given to the runner?
2. A hockey player makes a slap shot, exerting a force of 30.0 N on the hockey puck. The hockey stick is in contact with the puck for 0.16 s.
a) What impulse is given to the puck?
b) What is the change in momentum of the hockey puck?
3. From rest, a 10-kg block falls from a height of 2.0 m.
a) Find its velocity the instant it hits the ground. mgh = ½mv2
b) What is its change in momentum after the moment it hits the ground?
c) The block stops in 0.01 s. How much force is needed for this?
4. A 1200 kg car moving at 25 mph crashes into a barrier and stops in 0.001 s.
a) What is the change in momentum of the car?
b) How much force stops the car?
5. A Major League baseball pitcher can accelerate a ball from rest to 95 mph in about 2.0 seconds. If the mass of the baseball is 500 grams, how much force does a pitcher use to throw the baseball?
6. A Major League catcher stops a baseball in 0.001 s.
a) What is the change in momentum of the baseball?
b) How much force does the catcher use to stop the baseball?
Explanation / Answer
1) a) Change in momentum = 76*9.4 = 714.4 kg m/s b) force = 714.4/2.8 = 255.14 N c) impulse = 714.4 kg m/s 2) a) Impulse = 30*0.16 = 4.8 kg m/s b) Change in momentum = 4.8 kg m/s 3) a) Velocity = sqrt(2*2*9.8) = 6.261 m/s b) Change in momentum = 10*6.261 = 62.61 kg m/s c) Force = 62.6/0.01 =6261 N 4) a) Change in momentum = 1200*11.18 = 13416 kg m/s b) Force = 13416/0.001 = 13416000 N 5) Force = (42.47 m/s)*0.5/2 = 10.61 N 6) a) Change in momentum = 10.61*0.001 = 0.01061 kg m/s b) Force = 10.61 N
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