Q. The normal reaction on a body placed in a lift moving up with constant acceleration 2 $ms^{- 1}$ is 120 N. Mass of body is (Take $g = 10\ ms^{- 2}$)
A) 10 kg
B) 15 kg
C) 12 kg
D) 5 kg
Explanation
(a) From force diagram shown in figure,
[image:5_image290.jpeg]
$N - mg = ma_{0}$
or $120 - mg = 2m$
$\therefore m = \frac{100}{10 + 2}$
$= 10$ kg
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.