Question

A person of mass 50 kg stands on a weighing scale on a lift. If the lift is ascending upwards with a uniform acceleration of 9 $m{s}^{-2}$, what would be the reading of the weighing scale?
(Take g=10 $m{s}^{-2}$)

• A. 50 kg
• B. 60 kg
• C. 95 kg
• D. 100 kg

Answer 1

Answer: (C)

95 kg

The reading on the scale is a measure of the force on the floor by the person. By the Newton's third law this is equal and opposite to the normal force N on the person by the floor.
$\therefore$ When the lift is ascending upwards with a acceleration of $9m{s}^{-2}$, then
$N-50\times 10=50\times 9$
or $N=50\times 10+50\times 9=50(10+9)=950N
$\therefore$ The reading of weighing machine is 95 kg.