Question

A 12.0kg box is being pulled alone level ground at constant veloncity by a horizontal force of 38.0 newton .What is the cofficient of kinetic friction between the box and the floor?

Answer 1

Let's apply Newton's Second Law of Motion:

$$F_{pull}-F_{fr}=0,$$ $$F_{pull}=F_{fr}=\mu_k mg,$$ $$\mu_k=\dfrac{F_{pull}}{mg}=\dfrac{38\ N}{12\ kg\cdot9.8\ \dfrac{m}{s^2}}=0.32$$