According to me cotton will be more lighter as air is a fluid and Archimedes principal applies on it. As cotton occuies more volume it will feel more upthrust and more loss in weight. Therefore it if lighter.
The popular belief that buoyancy or the upthrust force only acts in case of a fall is false. Let's say you are underwater in a submarine and you step out of it into the water will you not get pushed up to the surface(if you don't apply any external force)? Every fluid has an upthrust force magnitude of which depends upon the density of the fluid. Now coming to the point. The atmosphere of earth is a fluid and therefore it offers an upthrust. The upthrust of course is more on the thing that occupies more space. In this case 1kg of cotton will obviously occupy more space than 1kg of iron and hence the upthrust on cotton will be more than the upthrust on 1kg of iron making the 1kg of cotton lighter than 1kg of iron. However in case of a vaccume both will weigh the same.
P.S - Rate this a "No" only if you have a counter valid explanation not because you think you're right.
1kg of iron. Bcoz atmospheric pressure on iron surface ís lesser than that on the cotton surface. Larger in the surface area greater is the atmospheri
c pressure and weight increases on
cotton. If the weighing is
perfom in the vaccuum,objects having same mass will have same weight.