Q. A body of weight $64\ N$ is pushed with just enough force to start it moving across a horizontal floor and the same force continues to act afterwards. If the coefficients of static and dynamic friction are $0.6$ and $0.4$ respectively, the acceleration of the body will be (Acceleration due to gravity $= g$)
A) $\frac{g}{6.4}$
B) $0.64\ g$
C) $\frac{g}{32}$
D) $0.2\ g$
Explanation
(d) Weight of the body $= 64\ N$
So mass of the body $m = 6.4\ kg,\ \mu_{s} = 0.6,\ \mu_{k} = 0.4$
Net acceleration = $\frac{Applied\ force - Kinetic\ friction}{Mass\ of\ the\ body}$
$= \frac{\mu_{s}mg - \mu_{k}mg}{m} = \left( \mu_{s} - \mu_{k} \right)g = (0.6 - 0.4)g = 0.2g$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.