Hydrogen baloon will varry which of the following most easily

 

a) 10kg feather

 

b)10kg cotton

 

c) 10kg iron

 

d) all of these

 

 

 

The wts given are not the actual ones !!!

 

They are all measured by a balance and the most voluminous the material more the force on it by air ( buoyancy ) and we weigh larger than the actual 10 Kg ( thinking that mass to be 10 kg )

 

Iron occupies smallest volume , hence less extra wt taken for it ,hence iron .