# Homework Help: Density and Force?

1. Nov 5, 2007

### rachelina

1. The problem statement, all variables and given/known data

The density of air is 1.29 kg per cubic meter.
The density of helium is 0.18 kg per cubic meter.
The density of hydrogen is 0.06 kg per cubic meter.
When inflated, a balloon has a volume of gas of 2.0 X 10^6 cubic meters.
When empty, the balloon has a mass of 200,000 kg.

HOW DO I FIND THE FORCE NECESSARY TO HOLD THE BALLOON DOWN IF IT WERE FILLED WITH HYDROGEN?

I have no idea what the equation would be. HELP!!!!

3. The attempt at a solution

Uhhhh....

2. Nov 5, 2007

### Astronuc

Staff Emeritus
Does one understand the concept of buoyancy, and effect of apparent weight or the impact of differential weight.

W = m g = $\rho$V g. The difference in weights would give the buoyant force and that is the force that would have to be provided by the tie down.

3. Nov 5, 2007

### rl.bhat

Find the total weight of the floating balloon. Find the weight of the displaced air. Difference of these weights will be the force necessary to hold the balloon down.