Physics education research, electronic materials, and the musings of Christopher Moore, Ph.D.

A 25 kg box is being pushed across the floor by a constant force ‹ 114, 0, 0 › N. The coefficient of kinetic friction for the table and box is 0.15. At t = 6.0 s the box is at location ‹ 10, 4, −4 › m, traveling with velocity ‹ 6, 0, 0 › m/s. What is its position and velocity at t = 7.7 s?

So to do this problem, I am using the change in momentum equation.  Right now I'm trying to find the net force.  I know the force of friction will be the coefficient of friction times the constant force, but do I have to add/subtract the gravitational force too??  Help!!!