Question

A railroad freight car with a mass of 50,000 kg is rolling along a level track at 0.30 m/s. A rope trails behind it. If the maximum force you could apply to stop the cart is 250 N, what is the shortest amount of time (measured in seconds) it would take for you to bring it to rest?

Answer 1

a = Fap/M = -250/50,000 = -0.005 m/s^2.

Vf = Vo + a*t = 0.
t = -Vo/a = 0.30/-0.005 = 60 s.