Your friend says that the buoyant force of the atmosphere on an elephant is significantly greater ...?

Question

than the buoyant force of the atmosphere on a small helium-filled balloon. What do you say? thanks for your help!!

Answer 1

That is true because elephant displaces larger volume and hence large weight of the atmosphere as compared to the balloon and the buoyant force is the weight of the fluid displaced by the body.

Answer 2

The elephant has more buoyant force because it has more surface area and higher internal pressure. Helium is the 2nd lightest gas and little pressure and the balloon is small.

Answer 3

Buoyant force is determined by displacement.  An elephant displaces more air than a balloon or a dog, so the force is higher.   But the elephant doesn't float because it is much denser than air and the air mass displaced does not come close to equalling the mass of the elephant.