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

Answer

C

Explanation

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