What is the maximum payload a helium balloon can lift at 0 degrees C?

[Minihoudini]

Homework Statement

a) a light balloon is filled with 400m^3 of helium at 0 degree C, the balloon can lift a payload of what mass?
b) what if? the density of hydrogen is nearly 1/2 the density of helium. what load can the balloon lift if filled with hydrogen?

answer A) 444Kg B) 480Kg

I have been trying various equations with buoyant force but none of them are giving me the answer I need

 

[jscushman]

a) a light balloon is filled with 400m^3 of helium at 0 degree C, the balloon can lift a payload of what mass?

The buoyant force is equal to the volume times g times the difference in densities between the two fluids (air and helium, in this case). This means that the mass of the payload will be equal to the volume times the difference in densities.

In this case, the density of air at 0˚C is 1.29 kg/m^3, and the density of helium is 0.18 kg/m^3, so the difference is 1.11 kg/m^3. This time 400 m^3 is the mass, 444 kg.

 

[Minihoudini]

thanks, I understand now.