Question

The density of iron is more than that of cotton .
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Answer 1

Now, density of cotton is less than that of iron. So, 1 kg of cotton will occupy more space than 1 kg iron, and hence displace more volume of air. And since upthrust is directly proportional to volume of fluid displaced, cotton will experience more upthrust than iron.

Answer 2

Yeah..u r right..

The density of iron is more than that of cotton .

The higher the density, the lower the volume. Iron occupies less volume than cotton, that's why it has higher density comparatively to Cotton.