The coefficients of static and kinetic friction between a 3.0-kg box and a horizontal desktop are 0.40 and 0.30, respectively. what is the force of friction on the box when a 15-n horizontal push is applied to the box

The force of friction on the box is 8.82 N.

The force of friction is given by the formula

F=μN

Here N is the normal force of the box=mg=3*9.8=29.4 N

Now the static friction force on the box is=0.4*29.4=11.76 N

Since the box is applied with the horizontal pull of 15 N, which is greater than the static friction, therefore the box must be in the moving condition, in that case there is dynamic friction force is applied on the box=0.3*29.4=8.8 N

Therefore the force of friction on the box is 8.8 N.