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need physics help - part2~

O

Omegachi

Diamond Member
here's another problem i am stuck on. pleasee help

A balloon is filled with helium at P=1 atm. If the balloon skin has a mass of 2.8kg, and its volume is 16m^3, What is the largest weight it can lift? (answer: mg =147N)


 
IIRC 1 mole of gas takes up 24 litres at STP.
16m^3 = 16000 litres so we have 666 2/3 moles of gas.

666 2/3 moles of Helium has a mass of 1.33 kg
666 2/3 moles of Air has a mass of approx. 19.25 kg (Assuming 78% Nitrogen and 22% Oxygen)

Difference is 17.92 kg. We also have the balloon skin having a mass of 2.8 kg.
Thus the total balloon is 15.12 kg lighter than the same volume of air.

15.12 * 9.81 = 148N of weight able to be lifted.

Your answer is 147N, so I'm guessing the make up of air you have been given is slightly different from the one I have assumed.
 
r u trying to get all your questions solved here ?
rolleye.gif
 
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