The idealized cycle shown is known as the Otto cycle. (Intro 1 figure) Suppose an engine is executing this Otto cycle, using a gas (not necessarily ideal) as its working substance. From state A to state B, the gas is allowed to expand adiabatically. (An adiabatic process is one in which no heat is added to, or given off by, the working gas.) The gas is then cooled at constant volume until it reaches state C, at which point it is adiabatically compressed to state D. Finally, it is heated at constant volume until it returns to state A. The pressure and volume of the gas in state A are p_A and V_A respectively. The pressure and volume of the gas in state C are p_C and V_C respectively. http://session.masteringphysics.com/problemAsset/1011140/12/STH_tc_2.jpg Part C What is DeltaU, the change in the gas's internal energy after a complete cycle? Express your answer in terms of any needed variables from the problem introduction. Okay I know that Q is zero, and deltaU = Q - W, so deltaU = -W, and W = p*deltaV, and a complete cycle means it returns to its original state. So my answer should be p_A*V_A, but it's incorrect, it says the answer does not depend on those variables, what variables are they looking for then? Help?