A man of mass 70 kg stands on a weighing scale in a lift which is moving upwards with a uniform spee

Question

A man of mass 70 kg stands on a weighing scale in a lift which is moving upwards with a uniform speed of 10 m/s. What would be the reading on the scale? (Take g = 10 m/s²)

Professor PC Thomas Classes · Answer

The lift is moving with a uniform speed, so acceleration a = 0. The reading on the scale is the normal reaction $R = mg = 70 	imes 10 = 700$ N.