Question

The weight of a man in a lift which is moving in upward direction with an acceleration ‘a’ is 680 N. When the lift moves in downward direction with the same acceleration, his weight is found to be 360 N. The real weight of the man is ______.

Options

• 390 N

• 440 N

• 520 N

• 630 N

Answer 1

The weight of a man in a lift which is moving in upward direction with an acceleration ‘a’ is 680 N. When the lift moves in downward direction with the same acceleration, his weight is found to be 360 N. The real weight of the man is 520 N.

Explanation:

In the 1^st case:

W₁ = mg + a    ...(i)

In the 2^nd case:

W₂ = mg − a    ...(ii)

Adding equations (i) and (ii),

2mg = W₁ + W₂

∴ mg = `(W_1 + W_2)/2`

= `(680 + 360)/2`

= `1040/2`

= 520 N