A person skateboarding is part of a closed system that has 1,450 J of mechanical energy. If the kinetic energy of the person increases from 200 J
to 825 J, what happens to the gravitational potential energy of the system?
O A. It decreases from 1,250 J to 625 J.
B. It decreases from 1,450 J to 1,025 J.
C. It increases from 1,250 J to 2,075 J.
O D. It increases from 625 J to 1,250 J.
I

An air standard cycle with variable specific heats is executed in a closed system and is composed of the following four processes. 1-2 isentropic compression 100 kpa and 22°c to 600 kpa 2-3 v=constant heat addition to 1500 k 3-4 isentropic expansion to 100 kpa 4-1 p=constant heat rejection to initial state (a) show the cycle on p-v and t-s s (b) calculate the net work output per unit mass (409 kj/kg) (c) determine the thermal efficiency (47.9%)