Where does the energy come from?

1. Jan 19, 2005

Omid

When a helium balloon soars into the sky, it gains KE and gravitational PE. where does that energy come from?

2. Jan 19, 2005

cepheid

Staff Emeritus
Best answer I can think of is that the balloon is being acted on by a buoyant force. Helium is less dense than air, and so the average density of the balloon is less than that of air. The balloon therefore "floats" in this sea of air called the atmosphere, and the buoyant force causes it to rise. Any corrections/clarifications?

3. Jan 19, 2005

Staff: Mentor

The lighter helium is bouyant in the denser air - the bouyant forces cause the helium balloon to rise with some velocity. Kinetic energy is simply 1/2 mv2.

The balloon is rising in the gravitational field, hence the mass of the balloon is gaining potential energy.

4. Jan 21, 2005

Omid

Thank you very much.