Two friends, Al and Jo, have a combined mass of 183 kg. At the ice skating rink,

Question

Two friends, Al and Jo, have a combined mass of 183 kg. At the ice skating rink, they stand close together on skates, at rest and facing each other. Using their arms, they push on each other for 1 second and move off in opposite directions. Al moves off with a speed of 7.5 m/sec in one direction and Jo moves off with a speed of 6 m/sec in the other. You can assume friction is negligible.

1)

What is Al's mass?

kg

2)

What is Jo's mass?

kg

3)

If you assume the force is constant during the 1 second they are pushing on each other, what is the magnitude of the force of Al on Jo?

N  

4)

If you assume the force is constant during the 1 second they are pushing on each other, what is the magnitude of the force of Jo on Al?

N  

Explanation / Answer

Momentum = mass * velocity

let us assume that mass of Jo = x kg

momentum by Al = Momentum by Jo

(183-x) * 7.5 = x * 6

x = 101.66kg,

a) Mass of Al = 180 - 101.66 = 81.33kg

b) Mass of Jo = 101.66kg

c) Magnitude of force of Al on Jo is given as

1kg = 9.8N,

81.33 * 9.8 = 797.034N

d) Magnitude of force of Jo on Al = 101.66 * 9.8 or 996.268N

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