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

Options

A. 15N
B. 49N
C. 24N
D. 74N

Answer

C

Explanation

When the lift is stationary, we get the true weight of the bag = 49N = mg
and the mass of the bag `=(mg)/(g)= (49)/(9.8)= 5kg`
When the lift moves downwards with an acceleration of 5 `m//s^(2)`, the net acceleration,
`g'= g-a=9.8-5=4.8m//s^(2)`
`therefore ` The weight `=mg'= 5xx4.8=24N`