Help is needed for questions B & C. Well-intentioned but bumbling Stuperman, at

Question

Help is needed for questions B & C.

Well-intentioned but bumbling Stuperman, at a muscular 90 kg, wants to stap a runaway train of mass 18,000 kg careening at 30 m/s. He decides the best course of action is to fly into it, head-on.

A) At what veloccity must he fly if the final velocity of the combined hero-train system is to be 0?

For this problem I used pi=pf and set m1v1+m2v2=0 since the final speed of the system will be zero.

90*v1 +18,000*30=0

v1= -6000 m/s

B) If the change in momentum occurs over 0.1 s, what average force will a 60 kg passenger experience? Assume the train doesn't vaporize.

C) About how many times greater than the passenger's weight (600n) is the average stopping force?

Explanation / Answer

time=0.1 s

mass of the passenger=60 kg

velocity=30 m/s, The train is hitting the person. So we need to consider the velocity of the train.

Force=m*v/t

Force=60*30/0.1=18000 N

c)initial speed=30 m/s

final speed=0 m/s

time=0.1 s

acceleration=30/0.1=300 m/s2

Force of the train=m*a=18000*300=5400000 N

5400000 N/600=9000 times

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