What will happen if you stick a helium balloon under water and release it?

Answer 1

It will accelerate rapidly to the surface of the water, and then continue to float upwards through the air, but with less acceleration. This is all due to the buoyant force. When an object is immersed in a fluid, the fluid exerts an upwards force equal to the weight of the displaced fluid. Of course, gravity still acts downwards on the object. But if the object is placed such that it displaces a volume of fluid with a greater weight than itself, as when the object is hollow or is less dense than the fluid, the net force is upwards. Helium is less dense than air, and is much less dense than water. Since water is more dense than air, the displaced volume of water weighs more than the displaced volume of air, so the buoyant force of the water is greater than that of the air. But it is always a net upwards force, so the balloon is always accelerating, until it reaches its terminal velocity. Terminal velocity is usually encountered with falling objects, but would also occur in an object accelerating upwards.

Answer 2

In theory, the baloon will rise to the surface, and continue upward.

However, in practice things can be a little different. Since the pressure under the water is much more than in air, the baloon would be much smaller than in air, because the He inside the baloon would have higher pressure and hence higher density. On the other hand, as the baloon rises above the surface, the pressure on the ballon at the top would fall really fast, while the pressure at the bottom will stay the same.

This will probably force the He inside compensate for the pressure difference pushing outward on the top much more than a baloon totally in air or totally in water. As a result, again probably the baloon will burst (from the top), since the structure cannot stand the difference in pressure.

Of course, this is provided that you manage to dip the baloon without popping it.

Answer 3

Same thing as if you stuck a balloon filled with air under water..
It would rise to the surface..
Except the helium baloon would continue to rise into the air
upon surfacing and the air filled balloon would just float on the waters surface.

Answer 4

All the above are wrong. Depends on how deep you put the helium (or air) balloon. As the depth increases the balloon shrinks & at some point will be stable - will neither rise nor sink. At this point the density of the balloon is the same as that of the water.

Answer 5

It will rise out of the water and up into the air.