you find a bag of cotton and an iron bar each indicating a mass of 100kg when measures on a weighing machine. in reality one is heavier than other. can you say which one is heavier and why?

Asked by ujjwalviky2003 | 23rd Dec, 2017, 06:05: AM

Expert Answer:

when an object is weighed in weighing machine, what actually we get is gravitational force acting on the body subtracted by the boyancy force acting on the body due to air. This boyancy force proportional to air density and volume of the object. In practical weight measurement, this boyancy force is neglected due to very low density of air in comparision with the density of materials we are using. But volume of 100 kg cotton is more in magnitude compare to 100 kg of iron. Since boyancy force is proportional to volume, more boyancy force is deducted from the real weight of cotton. Hence in reality, though weighing machine gives same 100 kg weight to iron and cotton, cotton is heavier than iron.

Answered by  | 23rd Dec, 2017, 11:00: AM