A 4 kg block has a coefficient of friction of 0.3 between itself and the surface it slides across. What is the friction force between the block and the surface?
a. 1.2 N
b. 4.3 N
c. 11.7 N
d. 13.3 N

C - 11.76 N (Newtons)

Explanation:

2 steps are needed,

First find the Force being applied by the box on the surface.

F = M(a) [Force equals: mass X Acceleration (of gravity)]

You get 39.2 N of Force.

Plug in the remaining values into the equation for Frictional Force

F(f) = μ(F) [Coefficient of Friction X Force applied by the Box]

So

F(f) = 0.3(39.2) = 11.76 N (of Frictional Force)

answer(20) psi;