As morning sunlight falls on a tethered helium balloon, it expands from a volume
ID: 2066559 • Letter: A
Question
As morning sunlight falls on a tethered helium balloon, it expands from a volume of 1.10 cross 103 m3 to a volume of 1.17 cross 103 m3.
If the initial temperature of the helium is 270 K, how much does the helium's internal energy increase?
Again, if the initial temperature of the helium is 270 K, how many joules of solar energy are absorbed?
NOTE: The following two questions were the first two questions that go along with this question. I already know how to do these, I just posted them for a reference.
How much work does the helium do on its environment (assuming that the balloon remains slack---i.e. P=Patm)?
W = PV
W = (1.013 X 105)(1.17 X 103 - 1.10 X 103)
W = 7.09 X 106 J or 7.09 MJ
And If the initial temperature of the helium is 270 K, how many moles of gas are in the balloon?
PV = nRT
(1.013 X 105)(1.1 X 103) = n(8.31)(270)
n = 4.97 X 104 moles
Explanation / Answer
W = P?V W = (1.013 X 105)(1.17 X 103 - 1.10 X 103) W = 7.09 X 106 J or 7.09 MJ Q=?U+W ?U=Q-W=nCv?T IF YOUR FINAL TEMP IS APPROX. SAME TO INITIAL THEN ?U=0 ANS A) 0 WHICH LEADS TO Q=W ANS OF B) Q=7.09 MJ
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