A person sitting in a chair with wheels stands up, causing the chair to roll backward across the floor. The momentum of the chair a. was zero while stationary and increased when the person stood.

b. was greatest while the person sat in the chair.

c. remained the same.

d. was zero when the person got out of the chair and increased while the person sat.

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.

Find the mass by adding the numbers from the three sliders

Why does a collision with an airbag cause less damage than a collision with a steering wheel