Question

A 60 kg man stands on a spring scale in the lift. At some instant he finds, scale reading has changed from 60 kg to 50 kg for a while and then comes back to the original mark. What should we conclude

• A. The lift was in constant motion upwards
• B. The lift was in constant motion downwards
• C. The lift while in constant motion upwards, is stopped suddenly
• D. The lift while in constant motion downwards, is suddenly stopped

Answer 1

The correct option is C

The lift while in constant motion upwards, is stopped suddenly

For retarding motion of a lift R = m(g + a) for downward motion

R = m(g – a) for upward motion

Since the weight of the body decrease for a while and then comes back to original value it means the lift was moving upward and stops suddenly.

Note: Generally we use R = m(g + a) for downward motion

R = m(g – a) for upward motion

Here a = acceleration, but for the given problem a = retardation