What is the work done by kinetic friction on a desk pushed on a rough surface?

[d.tran103]

Homework Statement

In the above problem, Amadeus pushed horizontally on a desk that rests on a rough wooden floor. The coefficient of static friction between the desk and the floor is 0.800 and the coefficient of kinetic friction is 0.620. The desk has a mass of 94.0 kg. He pushes just hard enough to barely get the desk moving and continues pushing with that force for 6.00 s. What work was done by the force of kinetic friction during this time?

Homework Equations

f=ma

The Attempt at a Solution

Hey, I've been working on this problem for an hour and can't figure this out. Can someone help me? Thanks!

 

[Doc Al]

What have you done so far?

One way to go is to figure out how far the desk travels in the given time. (Figure out the acceleration of the desk.)

 

[d.tran103]

Okay I got it now, my friend helped me. I was using the wrong formula.

a = sum of forces/sum of masses
a = us*mg – uk*mg/m
a = g(us – uk)
a = 9.8(0.800 – 0.620)
a = 1.764

d = ½*a*t^2
d = ½*1.764*6^2
d = 31.752

So, a = 1.764 and d = 31.752

F = us*mg
F = 0.800*94*9.8
F = 736.96

W = F*D
W = 736.96*31.752
W = 2.34e-4 Joules