Mechanical Engineering Answers

A compressed air vessels has inside diameter of 2m and a plate of 12.5mm.if tensile stress induced in plating is to be limited to 100mpa,calculate for both the longitudinal and circumferential seams the pre

The dielectric constant of Si is 11.9. What is the electronic polarisability due to the 

valence electrons per Si atom?

An ideal compressor compresses 12kg/min of air isothermally from 99kPa and a specific volume of 0.81m^2/kg to a final pressure of 600kPa. Determine a)power(kw) required to drive the compressor b. change in entropy(kJ/K) c. heat transferred

An adiabatic expansion of air occurs through a nozzle (W1=0) from 850 kPa and 75C to 140 kPa. For an isentropic expansion find: specific volume(m/kg), temperature(C) and velocity(m/s) at the exit section assuming initial kinetic energy is negligible

Assume 5ft/s of Hydrogen at 15 psia and 80F are compressed during an irreversible adiabatic process to 90 psia and 522F. For a non flow process determine a)k b)V c) W d)U and e)s

2lb/min of a certain gas whose R=767ft-lb/lb-R undergoes a steady flow isentropic process from 50 psia, 90ft/lb and 300ft/s until the pressure and velocity are doubled, and the volume is reduced by one third of its inital value. Determine a)H b)U c) Work

Consider that 2lb of air(R=53.342 ft-lb/lb-R and k=1.4) has a decrease of internal energy of 41.16 btu while its Fahrenheit temperature is reduced to one third of its inital temperature during a reversible nonflow constant pressure process. Determine a inital and final fahrenheit temperature b heat added c work d change in entropy

A cylinder of diameter d and length L is required to float in a liquid. How much L for the cylinder to float when its longitudinal axis being vertical? (specific gravity for cylinder and liquid are 0.7 & 0.9 respectively)

The Hall coefficient of certain silicon was found to be -7.35 x 10-5 m3

/C from 100 to 400 K. Determine the nature of the semiconductor. If the conductivity

was found to be 200 /m, calculate the density and mobility of the charge 

carrier.

The Fermi energy level for copper is 6.25 eV. Determine the temperature at 

which there is a 1% probability that an energy state 0.30 eV below the Fermi 

energy level will not contain an electron.