The n-p-n BJT has the following doping levels in the E, B and C: NDe = 1.8 e19 cm^-3, NAb = 1.7 e17 cm^-3, NDc = 4.5 e15 cm^-3. The electron drift velocity in the collector depletion region, vs = 1e7 cm/s. The intrinsic electron concentration in Si is 1e10 cm^-3. The relative dielectric permittivity of Si is 11.7. Find the collector depletion region delay time if the collector - base voltage is Vcb = 9 V. (Units: ps)

Asolid cylinder is concentric with a straight pipe. the cylinder is 0.5 m long and has an outside diameter of 8 cm. the pipe has an inside diameter of 8.5 cm. the annulus between the cylinder ad the pipe contains stationary oil. the oil has a specific gravity of 0.92 and a kinematic viscosity of 5.57 x 10-4 m2/s. most nearly, what is the force needed to move the cylinder along the pipe at a constant velocity of 1 m/s?