Question

A box has mass 13 kg and is at rest on a flat floor. A minimum force of 47 N is needed to push the box so it moves across the floor. What is the coefficient of static friction between the box and floor?

Answer 1

let's call
N=Normal force.
m*g=Weight.
F= Force needed to move the block.
f = friction force.
k = static friction coefficient.
For balance:
N = mg and F = f
By definition
f=k*N.
Clearing this last expression:
k=f/N.
Substituting:
k=f/N=F/m*g=(47)/((13)*(9.8))=0.37
the coefficient of static friction between the box and floor is 0.37