Question

If a body of mass $m$ is moving on a rough horizontal surface of coefficient of kinetic friction $\mu $ , the net electromagnetic force exerted by the surface on the body is

• A. $mg\sqrt{1 + \mu ^{2}}$
• B. $\mu mg$
• C. $mg$
• D. $mg\sqrt{1 - \mu ^{2}}$

Answer 1

Answer: (A)

As, normal force and friction force are the two electromagnetic forces acting on the body
The net electromagnetic force $=\sqrt{N^{2} + f^{2}}$
But $N=mg,f=\mu mg$
Force = $mg\sqrt{1 + \mu ^{2}}$