Suppose your mass is 80 kg, and the train comes to a uniform stop, going from 30

Question

Suppose your mass is 80 kg, and the train comes to a uniform stop, going from 30 meters per second to zero speed in a total of 6 seconds.

What is the acceleration a (a is the change of velocity with respect to a period of time) of the train as it comes to a stop and in what direction relative to the motion of the train?

Suppose you are in a seat belt and experience the same acceleration as the stopping train, how much force and in which directions are all the forces on you while you are seated and while the train is stopping?

What would happen to the force of the seat belt, in part c above, if the train were to stop suddenly in say ½ second? What does the impulse as related to stopping bodies predict?

Explanation / Answer

acceleration = chage in velocity/time = 0-30/6 = -5 m/s^2

f = ma = -80*4 = -400 N

impulse = f*t

I = 400*1/2 = 200 kg m/s

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