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 0.520 their own weight.

Question

and

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

Damon · Accepted Answer

acceleration = -.520(9.8) = -5.1 m/s^2
initial speed Vo = 65 km/hr(1hr/3600s)(1000 m/km)=18 m/s

From your physics text for constant acceleration
v = Vo + a t
here we have our initial Vo is 18 and we stop, v = 0
0 = 18 - 5.1 t
so t = 18/5.1 = 3.53 seconds

erin · Answer

i have one more How far does the train then travel while being slowed to a stop?

Damon · Answer

d = Vo t + (1/2) a t^2 d = 18 * 3.53 - (5.1/2)(3.53)^2

Damon · Answer

By the way, if you are really used to these problems you would just use the average speed during deacceleration (18/2 = 9 m/s) times the time (3.53 s)