Will mark in a heat engine, if 700 j of heat enters the system, and the piston does 400 j of work, what is the final internal (thermal) energy of the system if the initial energy is 1,200 j? 1,500 j 900 j 1,100 j 300 j explain your answer.

Answer(a)   the matererials that are in contact, the two materials and the nature of their surfaces/// (b)/// the force pushing the two surfaces together, pushing the surfaces together causes the more of the asperities to come together and increases the surface area in contact with each other

It is increased due to the doppler effect. (apex)