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?

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