Q.
A wooden box of mass 8 kg slides down an inclined plane of inclination 30${^\circ}$ to the horizontal with a constant acceleration of $0.4\ ms^{- 2}$. What is the force of friction between the box and inclined plane? [$\ g = 10\ ms^{- 2}$]
A) 36.8 N
B) 76.8 N
C) 65.6 N
D) 97.8 N
Explanation
(a) $ma = mg\sin{\theta - f}$
or $f = mg\sin{\theta - ma}$
$= 8\left\lbrack 10 \times \frac{1}{2} - 0.4 \right\rbrack$ N = 8$\times 4.6$N = 36.8 N
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.