How to find the change in momentum

[smalls]

Homework Statement

a shunting locomotive strikes a wagon of mass 8t and sets it in motion with an initial speed of 3.6m/s.The wagon travels freely along a level track against a track resistance of 58N/t for 12s.determine;

a.the frictional resistance(average force)
b.the reduced velocity of the wagon after the 12s due to the track resistannce

Please i need some one to help me figure out what to do first to start with this question..I'm not asking for answers,just want step by step procedure so i can get to understand this topic once and for all.:)

Homework Equations

F=Δmomentum(??)/time

struggling with how to find the change in momentum.:(

The Attempt at a Solution

 

[NascentOxygen]

Homework Equations

F=Δmomentum(??)/time

struggling with how to find the change in momentum.:(

Hi small s. You don't have to use momentum here, but you can if you wish.

F. Δt = m. Δv ... is a good equation here.

You know the frictional force acting on the moving wagon, and you are asked to determine its velocity after Δt of 12 seconds. So, go ahead.

First, address question (a).