Q. A body of mass $m$ rests on horizontal surface. The coefficient of friction between the body and the surface is $\mu$. If the mass is pulled by a force $P$ as shown in the figure, the limiting friction between body and surface will be
A) $\mu mg$
B) $\mu\left\lbrack mg + \left( \frac{P}{2} \right) \right\rbrack$
C) $\mu\left\lbrack mg - \left( \frac{P}{2} \right) \right\rbrack$
D) $\mu\left\lbrack mg - \left( \frac{\sqrt{3}P}{2} \right) \right\rbrack$
Explanation
(c) Normal reaction $R = mg - P\sin{30{^\circ}} = mg - \frac{P}{2}$
$\therefore$ Limiting friction between body and surface is given by, $F = \mu R = \mu\left( mg - \frac{P}{2} \right)$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.