A sample of an ideal gas in taken through the cyclic process abca in the given figure. It absorbs 50 J of heat during the parth ab, no heat during bc and rejects 70J of heat during ca, 40 J of work is done on the gas during the part bc.
(a) Find the internal energy of the gas at b adn c if it is 1500 J at a. ltbr. (b) Calculate the work done by the gas during the part ca.

Explanation

ab: `DeltaQ=DeltaU+DeltaW=U_b-U_a+DeltaW`
`50=U_b-1500+0impliesU_b=1550J`
bc: `DeltaQ=DeltaU+DeltaW=U_c-U_b+DeltaW`
`0=U_c-1550-40impliesU_c=1590J`
ca: `DeltaQ=DeltaU+DeltaW=U_a-U_c+DeltaW`
`-70=1550-1590+DeltaW`
`DeltaW=20J`