Chapter 9

NCERT
Class 9
Science
Solutions
2. You have a bag of cotton and an iron bar, each indicating a mass of 100 kg when measured on a weighing machine. In reality, one is heavier than the other. Can you say which one is heavier and why?

Question:

You have a bag of cotton and an iron bar, each indicating a mass of 100 kg when measured on a weighing machine. In reality, one is heavier than the other. Can you say which one is heavier and why?

Answer:

In reality, the cotton bag is heavier. This is because the cotton bag has more volume than that of an iron bar so it displaces more air and hence the buoyant force acting on the cotton bag due to the air is more than that acting on the iron bar (by Archimedes' principle) and True weight = Apparent weight + Buoyant force Apparent weight =  100  kg for both but buoyant forces are different.

Buy Latest Books

Teacher's Corner