The allowable stress in a steel shaft with an outside diameter of 1.5 in1.5\ \mathrm{in}1.5 in. and an inside diameter of 1.1 in1.1 \ \mathrm{in}1.1 in. is 12,000 psi12,000\ \text{psi}12,000 psi. What hp can the shaft deliver at 1750 rpm1750\ \mathrm{rpm}1750 rpm ?
The Fermi energy in metals is much higher than the thermal energy at typical temperatures. Why does this make the mean speed of conduction electrons nearly independent of temperature?
Although both the BF3\mathrm{BF}_3BF3 and NF3\mathrm{NF}_3NF3 molecules contain the same number of atoms, the BF3\mathrm{BF}_3BF3 molecule is flat, whereas the NF3\mathrm{NF}_3NF3 molecule is trigonal pyramidal. Explain.
Cell walls. Although these quantities vary from one type of Blo cell to another, a cell can be 2.0μm2.0 \mu \mathrm{m}2.0μm in diameter with a cell wall 50.0 nm50.0 \mathrm{~nm}50.0 nm thick. If the density (mass divided by volume) of the wall material is the same as that of pure water, what is the mass (in mg\mathrm{mg}mg ) of the cell wall, assuming the cell to be spherical and the wall to be a very thin spherical shell?