Magnitude of frictional force

Question

A 50kg wooden crate rests on a horizontal concrete floor.  the coefficient of friction is μ=0.7    What is the magnitude of the frictional force?

 

 

 

 

 

Answer 1

If the box has no other horizontal force acting on it, then there is no frictional force.

 

If there is, then F_f = μ·F_n.  Since the normal force balances out the weight, the magnitudes are equal.

 

F_n = mg

 

F_f = μmg = 0.7(50 kg)(9.8 m/s²) = 340 N

Answer 2

Megan

The magnitude of the frictional force is μ*W where μ=.7 and W=9.8*50=490N so frictional force is 340N at right angles to W

 

Jim