On finding kinetic energy? ? a skateboard is standing on top of a 4 meter half-pipe and is ready to jump onto the half-pipe. what is the skateboarder's kinetic energy?

The consumption of fossil fuels could be

Anybody wanna ? (picture included? )

Oxygen undergoes an isentropic expansion from 120 degree c and 280 kpa absolute to 140 kpa absolute. determine the final temperature of the oxygen and the amount of work per kg of o_2 produced in the process if it is adiabatic.