Okeep yourself warm in the winter, you heat a solid metal ball and place it on a stand in the center of your room. the ball has a radius of 20.0 cm and an emissivity of 0.790. if your room has a temperature of 15°c, what is the net power radiated by the ball initially, when the ball's temperature is 200°c?

A248-g piece of copper is dropped into 390 ml of water at 22.6 °c. the final temperature of the water was measured as 39.9 °c. calculate the initial temperature of the piece of copper. assume that all heat transfer occurs between the copper and the water. remember, the density of water is 1.0 g/m

As part of an industrial process, air as an ideal gas at 10 bar, 400k expands at steady state through a valve to a pressure of 4 bar. the mass flow rate of air is 0.5 kg/s. the air then passes through a heat exchanger where it is cooled to a temperature of 295k with negligible change in pressure. the valve can be modeled as a throttling process, and kinetic and potential energy effects can be neglected. (a) for a control volume enclosing the valve and heat exchanger and enough of the local surroundings that the heat transfer occurs at the ambient temperature of 295 k, determine the rate of entropy production, in kw/k. (b) if the expansion valve were replaced by an adiabatic turbine operating isentropically, what would be the entropy production? compare the results of parts (a) and (b) and discuss.

Which statement is best supported by the information in the chart? wave y is moving the fastest. wave x is moving the fastest. all of the waves are moving at the same speed. all of the waves have the same value of wavelengths per second.