*11.  A 1.00 x 102-kg crate is being pushed across a horizontal floor by a force  that makes an angle of 30.0° below the horizontal. The coefficient of kinetic friction is 0.200. What should be the magnitude of , so that the net work done by it and the kinetic frictional force is zero?

Free Body Diagram

 

We know mass is not moving in the vertical direction.

 

So the kinetic friction force is

 

So the work done by kinetic friction force is

 

 

The work done by the P force is

 

So the net work is

 

 

Either s = 0 or the term in the parenthesis is zero.

Factor out the P force

Solving for P

 

 

 

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This page last updated on January 11, 2020