Physics

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A 2.7 kg balloon is filled with helium ( density = 0.179 kg/m^3).
If the balloon is a sphere with a radius of 5.2m , what is the maximum weight it can lift?

• Physics -

Bouyancy is defined as the weight of the displaced fluid (in this case, air).

maxweight lifted=bouyancy-weight balloon-weight helium

= volume*densityair*g-2.7*g-volume(density helium)*g

= volume(densityair-densityhelium)g-2.7g

What does not make sense about that?
volume= 4/3 PI radius^3 I am not certain what to use for denstiy of air, as temperature is not given.

• Physics -

A balloon with a mass of 100 kg is filled with helium (density = 0.179 kg/m3). The balloon is spherical and has a diameter of 12.0 m. What is the maximum mass that can be attached to the bottom of this this helium balloon, for it to be able to fly? The density of air is 1.29 kg/m3.

For this question I got 67.5 kg, can you tell me if that is right, I did the procedure done above but the site I am on is telling me it is the wrong answer,

thanks!

• Physics -

It should be right. Did I tell you how to properly do the problem or DID I STUTTER!?