Question

A gas balloon absorbs 75 J of thermal energy.
The balloon expands but stays at the same
temperature. How much work did the balloon do
in expanding?

The equations is u=Q-W

Answer 1

Answer:

U1 = U2 since the temperature inside the balloon does not change

Q1 - W1 = Q2 - W2

Work done by the balloon = W2 - W1      (on the environment)

W2 - W1 = Q2 - Q1 = 75 J     heat put into balloon

So the balloon does 75 J on the environment