A spring balance is attached to the ceiling of a lift. A man hang… - Vidyadip

MCQ

A spring balance is attached to the ceiling of a lift. A man hangs his bag on the spring and the spring reads $49 \,N$, when the lift is stationary. If the lift moves downward with an acceleration of $5\,m/{s^2},$ the reading of the spring balance will be .......... $N$

A
$49$
✓
$24 $
C
$74$
D
$15 $

✓

Answer

Correct option: B.

$24 $

b
(b) When the lift is stationary $W = mg$

$⇒$ $49 = m \times 9.8$ $⇒$ $m = 5\,kg.$

When the lift is moving downward with an acceleration $R = m\,(9.8 - a) = 5[9.8 - 5] = 24N$

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