# Air Boyancy Question

1. Jul 30, 2006

### KingTutATL

A lighter than air balloon and its load of passengers and ballast are floating stationary above the eart. Ballast is the wieght that can be dropped overboard to make the balloon rise. The radius of this balloon is 6.25m. Assuming a onstant value of 1.29 kg/m^3 for the density of air, determine how much weight must be dropped overboard to make the balloon rise 105m in 15.0s?

I've been working on this one for a while and just keep getting nowhere!!

2. Jul 30, 2006

### Andrew Mason

What is the volume of the balloon? What is the mass of this balloon if it is floating stationary above the earth (not accelerating)?

What force is required for the balloon to rise 105 m in 15.0 seconds (careful: there is a bit of a trick, because the mass of the ballon accelerating depends on how much mass you drop overboard - work out an algebraic expression for the force in terms of the mass of the balloon and the mass jetisoned).

What mass must the balloon have in order to generate that buoyant force?

AM

3. Aug 1, 2006

### KingTutATL

How do I calculate the mass of the balloon while it is stationary. I guess it would be in equilibrium with the force of gravity and the bouyant force that oppose each other.

4. Aug 1, 2006

### Andrew Mason

If there is no acceleration, the buoyant force and the weight of the balloon balance. What does this mean for the mass of the balloon divided by volume?

AM

5. Aug 1, 2006

### KingTutATL

That they should equal the density of the air!