What are the equations for static and kinetic friction?

[homevolend]

Homework Statement

A box firstly at rest on a horizontel surface, needs a horizontal force to get it in motion. Though after in motion the box needs a force to keep in speed. Find static and kinetic coefficient of frictions.

Homework Equations

fk=mukFn
Fs=musFn

The Attempt at a Solution

I solved!

 

[True Cherokee]

Try drawing a free body diagram so you can see everything a little bit more clearly. After that, just try and figure out what you need to meet the specifications of your problem. If the forces are unbalanced, F_app does not equal F_f.