Question

A body of mass 32 kg is suspended by a spring balance from the roof of a vertically operating lift and going downward from rest. At the instant the lift has covered 20 m and 50 m, the spring balance showed 30 kg and 36 kg respectively. Then the velocity of the lift is(a) decreasing at 20 m, and increasing at 50 m(b) increasing at 20m and decreasing at 50 m(c) continuously decreasing at a steady rate throughout the journey(d) constantly increasing at constant rate throughout the journey.

Answer 1

A body of mass 32 kg is suspended by a spring balance from the roof of a vertically operating lift and going downward from rest. At the instant the lift has covered 20 m and 50 m, the spring balance showed 30 kg and 36 kg respectively. Then the velocity of the lift is(a) decreasing at 20 m, and increasing at 50 m(b) increasing at 20m and decreasing at 50 m(c) continuously decreasing at a steady rate throughout the journey(d) constantly increasing at constant rate throughout the journey

Answer 2

Answer:

the acceleration is upto 20m and decreasing at 50m

Explanation:

Mass of the body = 32kg

Lift has covered = 20 m and 50 m,

Spring balance shows = 30 kg and 36 kg

N = m (g-a), N<mg if a is downwards and N>mg if a is upwards

Reading of the spring balance is less than m if a is downwards and reading of balance is greater than m if a is upwards

For the downward journey, first case  -

32g-30g = 2g

= 32a so

a = g/16

Second case  -

32g-36g = -4g

= 32a so

a = -g/8

Thus, the acceleration is upto 20m and decreasing at 50m