Q. A rupee coin starting from rest rolls down a distance of 1 m on an inclined plane at angle of $30{^\circ}$ with the horizontal. Assuming that $g\ = \ 9.81$ $ms^{- 1}$, time taken is

A) 0.68 s
B) 0.6 s
C) 0.5 s
D) 0.7 s
Explanation

(d) Here, $l = 1m,\ \theta = 30{^\circ},\ g = 9.81\ \ ms^{- 2},\ t = ?$
$t = \sqrt{\frac{2l(1 + K^{2}/R^{2})}{g\sin\theta}}$
For a rupee coin, $K^{2} = \frac{1}{2}R^{2}$
$t = \sqrt{\frac{2 \times 1(1 + 1/2)}{9.81\sin{30{^\circ}}}} = \sqrt{\frac{6}{9.81}} = 0.78\ s$

Dr. Abubacker
Reviewed by Dr. Abubacker

Physics Educator & NEET/JEE Specialist

Ph.D. in Physics with 19+ years of teaching experience.