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## Homework Statement

Find the speed at which Superman (mass=89.0 kg) must fly into a train (mass = 17755 kg) traveling at 85.0 km/hr to stop it.

Running into the train at that speed would severely damage both train and passengers. Calculate the minimum time Superman must take to stop the train, if the passengers experience an average horizontal force of 0.410 their own weight

How far does the train then travel while being slowed to a stop?

## Homework Equations

p=mv

F=dp/dt

F=ma

J= p2-p1

J=F(t2-t1)

## The Attempt at a Solution

I found the speed at which superman should fly by

m1v1=m2v2

17755*85.0=89.0*v2

v2=1.70×10^4 km/hr

for the minimum time this is what I do, but I got it wrong

since J=F(t2-t1)

and J=p(final)-p(initial)

then J=mv-mv

J=(89)(0)-(89)(1.70×10^4)

J=1513000

J=F(t2-t1)

1513000=(.41)(t)

t=3.68x10^6hr

then for the distance I couldn't calculate it because I had no idea what the time is