Astudent holds two lead weights, each of mass 6.4 kg. when the students’ arms are extended horizontally, the lead weights are 0.84 m from the axis of rotation and the student rotates with an angular speed of 2.4 rad/sec. the moment of inertia of student plus stool is 9.4 kg m2 and is assumed to be constant; i. e., the student’s arms are massless! then the student pulls the lead weights horizontally to a radius 0.23 m from the axis of rotation.
1). find the new angular speed of the student?
2). find the kinetic energy of the rotating system (comprised of student, stool, and weights) before and after he pulls the weights inward?

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.

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What’s #16 asking and how do i solve it?