The internal energy of a gas is 900 J. The gas is compressed adiabatically, and its volume decreases by 100 cm3. If the pressure applied on the gas during compression is 1 atm, what is the internal energy of the gas after the adiabatic compression?
The answer is 890 J, but I don't understand why.
Ei= 900J
Ef: ?
Q= 0
Ef - Ei = Q - W
Ef= Ei - W
W= p (Vf-Vi)
P=1 atm= 10^5 Pa
This is how the answer is solved.
Ef= 900J - 10^5Pa * 100 (10^-2)^3
Ef=890J
However, since it says the volume decreases by 100 cm3 shouldn't the work be negative?
In terms of Vf-Vi the answer there should be -100cm3 not +100cm3 since the initial volume has lost 100 cm3.
Ef= 900J + 10^5Pa * 100 (10^-2)^3
Ef=910 J
This is the wrong answer that I get.
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