1-ft3 of air is contained in a spring-loaded piston-cylinder device. the spring constant is 6lbf/in, and the piston diameter is 12 in. when no force is exerted by the spring on the piston, the state of the air is 250 psia and 450◦f. this device is now cooled until the volume is one-third its original size. determine the change in the specific internal energy and enthalpy of the air.

Which of the following characteristics of earth's relationship to the sun explains the existence of earth's seasons? choose all that apply. earth has a satellite called the moon, which rotates around earth. earth spins on its axis, completing one rotation each day. earth's axis always points in the same direction relative to the stars. earth's axis is tilted relative to its orbital plane. earth orbits around the sun, completing one orbit each year.