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 these

Answer 1

Answer: (A)

720 N and 480 N

Answer 2

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