Samples of different materials, A and B, have the same mass, but the sample of A is higher in density. Which statement could explain why this is so?

A. The particles that make up material B have more mass than the
particles that make up material A.
B. The particles that make up material A have more mass than the
particles that make up material B.
C. The sample of material A has greater volume than the sample of
material B.
D. The particles that make up material B are more closely packed
together than the particles that make up material A.

Find the volume of the ellipsoid x^2+y^2+5z^2=36.

Identical marbles are released from the same height on each of the following four frictionless ramps . compare the speed of the marbles at the end of each ramp. explain your reasoning

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.