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)

720 N and 480 N

Answer 2

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) $\, \, \, \, \, \, \, \, =60(10-2)=60 \times 8$ $\, \, \, \, \, \, \, \, =480N$