Question

1. Explain why a balloon filled with helium gas rises in air. Why does the balloon rise to a particular height above ground and does not rise further ?

Answer 1

1. Helium gas is lighter than air. So when a balloon is filled with helium, it rises in the air.

Helium is light, but not the lightest. (The lightest gas is Hydrogen) Also the atmospheric limit of the gas is only upto a certain height, after which the balloon does not rise further.

Answer 2

$\huge \fbox{Answer}$

The balloon with helium rises up initially because, upthrust is more initially in comparison to its weight. As the density of air gets reduced with height, the upthrust reduces and at a point gets balanced by the weight. So it does not rise beyond the height.