Question

a wagon of mass 2000kg is seperated from a train travelling at 9km/h and the wagon comes to rest in 2 min.find resistance between the wheels of the wagon and the track...do the sum

Answer 1

Since the wagon was connected to the train before, it's initial velocity is the same as the train which 9km/hr

1 km/hr = (5/18) m/s
9km/hr = 2.5 m/s

It comes to rest, so it's final velocity is 0 m/s

It takes 2 min = 120 seconds to get to rest.

a = (0-2.5)/120
a = -0.02083 m/s^2

So the retarding force applied is

F = ma
F = (2000)×(-0.02083)
F = -41.667 N

So a force with a magnitude of {41.667 N} was applied in the direction opposite to the velocity of the wagon to bring it to rest in 2 min from an initial velocity of 9 km/hr by producing a deceleration of {0.02083 m/s^2} in it.