Need help finding coefficient of kinetic friction

[zinniagirl]

Homework Statement

A horizontal force of 150 N is used to push a 40.0 kg packing crate a distance of 6.00 m on a rough horizontal surface. If the crate moves at constant speed, find the coefficient of kinetic friction between the crate and the surface.

Homework Equations

fK= coeff. of kin. friction X N
Fy= -mgy + normal force

The Attempt at a Solution

I started by using Fy= -mgy + N to be 0= -40 (9.8) (cos 0) + N and found N be 392. But now I'm not sure where to go from here to find the coefficient of kinetic friction. Can anyone help?

 

[rock.freak667]

Constant speed means the resultant force is zero...so what is the value of the frictional force?

 

[zinniagirl]

Constant speed means the resultant force is zero...so what is the value of the frictional force?

150 N. So the coefficient of kinetic friction would then be .38, correct?

 

[rock.freak667]

Yes that should be correct.

 

[zinniagirl]

Thanks!