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     AIEEE  Solved  Paper-2003

A) 24 N  

B)                                       74 N      

C)       15 N                      

D) 49 N

Correct Answer: A

Solution :

In stationary position,         spring balance reading                                 = mg = 49                     \[m=\frac{49}{9.8}=5\,kg\] When lift moves downward                     mg - T = ma                 Reading of balance                                     T = mg - ma                                  = 5 (9.8 ? 5)                     \[=5\times 4.8\]                     = 24.0 N