Question

A woman weighing 50 kg stands on a weighing machine placed in a lift. What will be the reading of the machine in the following cases ?1) when a lift is moving upward with a uniform velocity of 5m/s.2) when the lift is moving downwards with a uniform accelartion of 1m/s. [g=10 m/s^2]

Answer 1

Mass of woman, M=50 kg
(1) When lift is inn uniform motion ,acceleration of woman ,a=0
apparent wight = actual weight
Reading of machine , R= Mg =$50kg\times 10m/s^2=500N$ or 50kg wt.

(2) When lift is moving downwards with uniform acceleration 1m/s² (say a)
Apparent weight is less than actual weight
Reading of machine ,R =M(g-a)=$50\left(10-1\right)=450N$ or 45kg wt.