1) Two 1.5 kg balls move away from each other, one traveling 4 m/s to the right,

Question

1) Two 1.5 kg balls move away from each other, one traveling 4 m/s to the right, the other 2 n1/s to the left. What is the magnitude of the total momen- tum of the system? Answer in units of kg - n1/ s

2) Two 1400 kg cars drive east; the ?rst moving at 50 m/s, the second at 25 m/s. What is the magnitude of the total momen tum of the system? Answer in units of kg - n1/s

3) A barefoot ?eld-goal kicker imparts a speed of 42 m/s to a football initially at rest. If the football has a mass of 0.65 kg and the time of contact with the ball is 0.018 s, what is the magnitude of the force exerted by the ball on the kicker

Explanation / Answer

1) total momentum = sum of mv = 1.5*4 - 1.5*2= 3.0 kgm/s

2) total momentum = sum of mv = 1400*50 + 1400*25= 1.05E5 kg m/s

3)

F = dp/dt = m v/dt = 0.65*42/0.018= 1517 N

4)
108 km/hr = 30 m/s

dp = m v = 921*30= 27630 kg m/s

5) F = dp/dt = 27630/0.933= 29614 N

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