Finding the Coefficient of Kinetic Friction

[curser656]

Homework Statement

A worker at a moving company places a 252kg trunk on a piece of carpeting and slides it across the floor at a constant velocity by exerting a horizontal force of 625 Newtons on the trunk.

a) What is the Coefficient of Kinetic Friction?

b) What happens to the coefficient of kinetic friction if another 56kg trunk is placed on top of the 252kg trunk?

c) What horizontal force must the mover apply to move the combination of the two trunks at a constant velocity?

Homework Equations

F=MA
Ffriction=µFnormal

The Attempt at a Solution

I have absolutely no idea how to find the coefficient of kinetic friction because I am only able to get force normal by using Fg=mg because its not moving up or down so Fn and Fg are equal. That's about it. Thankz

 

[Redsummers]

If the velocity is constant, it means that a=0, right?
So what would that mean if we apply that on ΣF=ma?