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 \[T=mg-ma\] \[=5(9.8-5)\] \[=5\times 4.8\] \[=24\,\,N\]