Ashaft of solid circular section has a diameter of 30 mm. the allowable shear stress in the material is 50 mpa. determine the power that can be transmitted at 2000 rpm through the shaft.

An inventor claims to have developed a reversed heat engine (ie. a heat pump) which is able to deliver 10 kj heat into the room at 20°c from outside ambient temperature of -10°c by consuming only 2 kj electricity in winter. this claim is a)-impossible b)-possible only if the heat pump is ideal c)-practically possible d)-unable to be assessed as it depends on the working fluid used in the heat pump.