Maximum angle for pushing a box with friction at constant velocity

[juliesangelcleo]

someone is puchsing a box across a floor at a constant velocity. The coefficient of kinetic friction is .41. THe pushing force is directed downward at an angle below the horizontal. If the angle is greater then a certain value then no matter the force the box can not be moved. What is this angle.

I really have no clue where to start

 

[Almoore01]

Here's a tip:

I really have no clue where to start

First you need to draw a force diagram for the box and from there, solve for the Normal Force. Is the magnitude of the force on the box given in the problem?

 

[mjsd]

then think about under how the net force of the system may becomes zero (ie. box doesn't accelerate)