Question

A $60$ kg man stands on a spring balance in a lift. At some instant, he finds that the reading on the scale has changed from $60$ kg to $50$ kg for a while and then comes back to the original mark. What is his conclusion?

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

Answer 1

The correct option is D The lift while in motion upward suddenly stopped

For a moment, the weight decreases to 50 kg from 60 kg but again comes back to original. If the lift is moving upward with an acceleration a, then apparent weight is W= m(g+a).

If the lift suddenly stops during upward motion, then apparent weight is m(g-a). Retardation will take place due to sudden jerk for sudden stop. Therefore weight decreases for a moment and again comes back to original value.