A helium filled baloon in my room rose to the ceiling because it is lighter than air. But after some time the baloon gradually fell to the floor. Why does it cease to rise after some time?
@Physics

Question

A helium filled baloon in my room rose to the ceiling because it is lighter than air. But after some time the baloon gradually fell to the floor. Why does it cease to rise after some time?
 @Physics

nottim · Answer

the helium particles stopped moving as quickly?

anonymous · Answer

hmmm. why would they? the temperature of the room didnt change dramatically. But assuming that it did, would slower moving particles make the gas(helium) more dense?

anonymous · Answer

the balloon rises coz it is lighter than air first.
then the ultra small Helium atoms escape from the balloon's rubber membrane.
as the gas is lost, Buoyant force of air decreases and the balloon starts to fall down!!!!!!!!

anonymous · Answer

akshay's answer is good.this happens bcoz the pressure outside the balloon is high,since it contains a mixture of gases.by the process of diffusion air enters the balloon ,hence relatively it's density increase.and it stops going high.
     this principle might be followed in hot air balloons.but here after rising to a certain height heating is stopped so that it's pressure is relatively equal to that of the atmosphere.