Question

A man squatting (sitting) on a weighing machine, gradually stands up and then becomes stationary. The reading of weighing machine during this process will be :

• A. constant and equal to mg in magnitude
• B. constant and greater than mg in magnitude
• C. variable but always greater than mg
• D. Initially greater than mg, then less than mg, and then becomes constant equal to mg

Answer 1

The correct option is D Initially greater than mg, then less than mg, and then becomes constant equal to mg

Answer is D.
Initially there is +ve acceleration, a. So net force will be= m(g+a) and therefore greater than mg.
When he gradually stands up, acceleration decreases. So net force will be= m(g-a) and therefore less than mg.
And finally man becomes stationery so reading of weighing machine will be equal to mg.