Question

A man of mass 60 kg is riding in a lift. The weight of the man, when the lift is accelerating upwards and downwards at 2 $ms^{-2}$, are respectively .
(Taking g = 10 $ms^{-2})$

• A. 720 N and 480 N
• B. 480 N and 720 N
• C. 600 N and 600 N
• D. None of the above

Answer 1

Answer: (A)

When the lift is accelerating upwards with a constant acceleration a, then
weight, w = m(g + a)
$ \, \, \, \, \, \, \, = 60 (10+2) = 60 \times 12$
$ \, \, \, \, \, \, \, \, = 720N$
When the lift is accelerating downwards at the rate a, then
weight, w' = m(g - a)
$ \, \, \, \, \, \, \, \, =60(10-2)=60 \times 8$
$ \, \, \, \, \, \, \, \, =480N$