Calculating Diameter of Balloon to Lift 20 Metric Tons

[xenoflauge]

Homework Statement

balloons are required to lift 20 metric tons. the pressure of helium is 101.325kpa. temp=21.1degcelsius.

what should be the diameter of the balloon if it was spherical in shape in order to lift the weight?

Homework Equations

buoyant force??

The Attempt at a Solution

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tnx.

 

[berkeman]

You need to show more work in order for us to help you. Tell us more about buoyant forces. What causes them? If you have an object that normally floats in water, and you hold it under water, how do you calculate the upward force that you feel from the object?