How Much Force to Overcome Static Friction and Move a Crate?

[wcbryant87]

Homework Statement

The weight of the crate is 875 N. You push it with a force of magnitude 300 N but it doesn't move

What is the magnitude F_p of the minimum force you need to exert on the crate to make it start sliding along the floor? Let the coefficient of the static friction $$\mu$$_s coefficient the crate and the floor be 0.56 and that of kinetic friction, $$\mu$$_k, be 0.47

Homework Equations

The Attempt at a Solution

I tried solving it by using the formula f_k = $$\mu$$_kn but it told me that I'm going about the problem wrong. It says that I need to study the condition for which the crate ceases to be at rest, that is, the condition for which static friction ceases to be valid. I used kinetic friction though, so I don't know what to do now.

 

[Delphi51]

Use the static coefficient of friction in your formula.
Once it has started moving, the lower dynamic coefficient comes into play and a smaller force will suffice to keep it moving.