the aurora borealis or northern light occur when solar flares react with the atmosphere near the north poles. the aurora give off colred light because electricity is flowing. which state of matter must the air be in

An ideal otto cycle has a compression ratio of 10.5, takes in air at 90 kpa and 40°c, and is repeated 2500 times per minute. using constant specific heats at room temperature, determine the thermal efficiency of this cycle and the rate of heat input if the cycle is to produce 90 kw of power.

The man of mass m1 and the woman of mass m2 are standing on opposite ends of the platform of mass m0 which moves with negligible friction and is initially at rest with s = 0. the man and woman begin to approach each other. derive an expression for the displacement s of the platform when the two meet in terms of the displacement x1 of the man relative to the platform.

A58-kg boy swings a baseball bat, which causes a 0.140-kg baseball to move toward third base with a velocity of 38.0 m/s.