Q. A block can slide on a smooth inclined plane of inclination $\theta$ kept on the floor of a lift. When the lift is descending with a retardation $a$, the acceleration of the block relative to the incline is
A) $(g + a)\sin\theta$
B) $(g - a)$
C) $g\sin\theta$
D) $(g - a)\sin\theta$
Explanation
(a) Acceleration of block in a stationary lift $= g\sin\theta$
If lift is descending with acc. then it will be $(g - a)\sin\theta$ but in the problem acceleration $= \ - a$ (retardation)
$\therefore$ Acceleration of block $= \left\lbrack g - ( - a) \right\rbrack\sin\theta = (g + a)\sin\theta$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.