# Finding F required pushing a box at angle (theta) for constant v

1. Oct 17, 2011

### Eats Dirt

1. The problem statement, all variables and given/known data

a crate with mass m rests on a horizontal floor. a woman pushes down at an angle of theta below the horizontalon the frace with a force F, the coefficient of kinetic friction is Uk.
a) what magnitude of force F is required to keep the crate moving at a constant velocity?

2. Relevant equations

Ff(frictional force)=UkFn

Constant velocity which means Fnet=0

3. The attempt at a solution

since Fnet is 0 you can set horizontal force = to frictional force

Ff=Fsin(theta)
Uk(mg + Fcos(theta))=Fsin(theta)
(Uk(mg+ Fcos(theta))/sin theta = F

This is apparently not right and i cant thing of what else to do -_- help would be very much appreciated as well as an easier way of approaching problems with only symbols.
thanks!

Last edited: Oct 17, 2011
2. Oct 17, 2011

### DukeLuke

You are very close, but I think you mixed up the components of F. I think your cos and sin should be switched.