Q. A body of mass 40 kg resting on a rough horizontal surface is subjected to a force $P$ which is just enough to start the motion of the body. If $\mu_{s} = 0.5,\mu_{k} = 0.4,g = 10\ ms^{- 2}$ and the force $P$ is continuously applied on the body, then the acceleration of the body is
A) Zero
B) 1$\ ms^{- 2}$
C) 2$\ ms^{- 2}$
D) 2.4$\ ms^{- 2}$
Explanation
(b) $P = f_{ms} = \mu_{s}mg$
When the body starts moving with acceleration $a$, then
$P - f_{k} = ma$
$\mu_{s}mg - \mu_{k}mg = ma$ or $a = (\mu_{0} - \mu_{k})g$
or $a = (0\text{.}5 - 0.4)10$
$= 0.1 \times 10ms^{- 2} = 1ms^{- 2}$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.