Engineering Answers

1. Given F= (k₁/r)a_r+(k₂z)a_{z ,} Evaluate the scalar surface integral of the over a surface of a closed cylinder about the z-axis specified by z=±3 , r=2.

1. The electric potential (V) in a region of space in volts is given by

V=5x-7x²y+8y²+16yz-5z , where distances are measured in meter. Calculate the y-component of the field at point (2 4 -3).

One kilogram of gas at an initial pressure of 0.11 MN/m² and a temperature of 15⁰C.

It is compressed isothermally until the volume becomes 0.1 m³ .Determine

a) the final pressure

b) the final temperature

c) the heat transfer

If the compression had been adiabatic, determine

d) the final pressure

e)the final temperature

f) the work transfer

An engine has a swept volume of 15 litres and a volume ratio of compression of 14:1. The air in the engine at the beginning of compression has a temperature and pressure of 30⁰C and 95 kN/m², respectively. The air is compressed according to the law PV^1.34=C At the end of the compression the air is heated at constant volume through a pressure ratio of 1.6:1. Determine

a)the temperature and pressure of the air at the end of the compression

b)the temperature and pressure of the air at the end of the constant volume process

c)the heat transfer required to carry out the constant volume process

For the air, take c_p = 1.005 KJ/kg K, R = 0.24 KJ/kg K

0.21 kg of gas is heated by means of an electric heater for a period of 10 mins during which time the pressure of the gas remains constant. the temperature of the gas is increased from 16⁰C to 78⁰C. the power used by the heater is 20 watts assuming no losses determine

a)the specific heat capacity of the gas at constant pressure

b)the specific heat capacity of the gas at constant volume

c)the characteristic gas constant

d)the density of the gas at a temperature of 160 C and with a pressure of o.12MN/m2

for the gas, take y=1.38

0.23 kg of air has an initial pressure of 1.7 MN/m² and a temperature of 200⁰C. It is expanded to a pressure of 0.34MN/m² according to the law PV^1.35 = constant. determine the work transfer during the expansion. take R= 0.29 kj/kg K

A mass of gas has an initial pressure and temperature of 0.11 MN/m² and 15⁰C. respectively. It is compressed according to the law PV^1.3 = constant until temperature becomes 90⁰C temperature becomes 90 oc. Determine the final pressure of the gas.

A quantity of gas has an initial volume and temperature of 1.2 litres and 150⁰C respectively.  It is expanded to a volume of 3.6 litres according to the law PV^1.4 = constant Determine the final volume of the gas.