1 Kg iron and 1 Kg cotton can weigh same in vacuum but not in air. The answer to that is very factual, yet most of us do not know about it. 1 Kg cotton weigh slightly less than 1 kg iron. Here’s how.
- Since density of cotton is lesser than iron, the total volume of 1 kg cotton will be higher than 1 kg iron. You can see the difference in the pictures.
- Therefore, 1 kg cotton, with more volume, will shift more air than 1 kg iron.
- As a result, an upward force called buoyant force will be exerted on the cotton by the fluid (liquid or gas) in which it is placed. This buoyant force will be larger on cotton than on iron as it is equivalent to the weight of the fluid being displaced.
- This causes a slight decrease in cotton weight.
Now you know the answer, go and impress your science professor.
Bonus: Check out the following scientific experiment that demonstrates a similar concept: