posted by april .
An empty rubber balloon has a mass of 0.0100 kg. The balloon is filled with helium at a density of 0.181 kg/m3. At this density the balloon is spherical with a radius of 0.300 m. If the filled balloon is fastened to a vertical line, what is the tension in the line?
nevermind. got it.
Tension = Bouyancy force - ballon weight - helium weight.
= [V(air density - helium density) + ballon mass)]*g
V = (4/3) pi R^3
g = 9.8 m/s^2
By multiplying by g, you get the answer in Newtons, which is probably what they want.
For the air density, which you need, they should have told you what Temperature and pressure to assume. Use the STP value.