Question

A horizontal force of 21 N is applied to a 20 kg block lying on a horizontal surface. Find the acceleration of the block, if the coefficient or kinetic friction is 0.10.

Answer 1

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

$$F_{h}-F_{fr}=ma,$$ $$F_{h}-\mu_kmg=ma,$$ $$a=\dfrac{F_{h}-\mu_kmg}{m},$$ $$a=\dfrac{21\ N-0.1\cdot20\ kg\cdot9.8\ \dfrac{m}{s^2}}{20\ kg}=0.07\ \dfrac{m}{s^2}.$$