Under some circumstances, a star can collapse into an extremely dense object made mostly of neutrons and called a neutron star. the density of a neutron star is roughly 1014 times as great as that of ordinary solid matter. suppose we represent the star as a uniform, solid, rigid sphere, both before and after the collapse. the star's initial radius was 7.0×105 km (comparable to our sun); its final radius is 17 km.

if the original star rotated once in 35 days, find the angular speed of the neutron star.

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.

=force × distance a. work b. velocity c. pressure d. momentum

Which component of the earth’s atmosphere is decreased due to photosynthesis?