question_answer

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

A)  24 N                                     

B)  74 N

C)  15 N                     

D)         49 N

Correct Answer: A

Solution :

In stationary position, spring balance reading                 \[=mg=49\]                 \[m=\frac{4.9}{9.8}=5\,\,kg\] When lift moves downward.                 \[mg-T=ma\] Reading of balance                 \[T=mg-ma\]                 \[=5(9.8-5)\]                 \[=5\times 4.8\]                 \[=24\,\,N\]