Mechanical Engineering Answers

2. Water of m = 5 kg m , P = 1 MPa, H = 10,280 kJ. Determine temperature, total volume, total

internal energy and total entropy.

1. Steam at a temperature of 240 o C has a specific volume of 0.15436 m 3 /kg. Determine

pressure, specific internal energy, enthalpy and entropy.

The angular acceleration of an rotating body is define by the relation 𝔞 = - kθ. Determine a)

the value of k if angular velocity is 8 rad/sec at angular displacement of 0 radian and angular

velocity is 0 rad/sec at angular displacement of 4 radian. B) find the angular displacement at

angular displacement of 3 radian.

ii. A mass of gas is stored in a cylinder. The gas is stored at a pressure of 1.2 MPa and the cylinder has a volume of 0.03 m3 and temperature of 100 oC , Find the mass of the gas.

The characteristic gas constant for air is 300 Jkg−1K−1.

i. A fixed mass of gas has a pressure of 1.2 MPa and volume of 0.3 m3 and temperature of 100 oC . The pressure is changed to 400 kPa and the volume changed to 0.06 m3.

Determine the new temperature?

Calculate the efficiency of an ice making machine that takes in water at 10°C and produces ice at a temperature of -7°C. Water is taken in at a rate of 1 kg every 4 minutes. The input power of the machine is 400 W. The specific heat capacity of water is 4187 Jkg−1K−1 and its specific latent heat of fusion is 334 Jkg−1.

A brass tie bar of length 500 mm and diameter 20 mm undergoes a change in temperature

from 25°C to 135°C. The linear expansivity of copper is 19 × 10−6°C−1 and its modulus of

elasticity is 84 Gpa.

i) Determine the change of length that takes place.

ii) Determine the compressive force induced in the bar if it is rigidly held and expansion is prevented.

a prismatic steel bar of 50 by 50 mm square cross section is subjected to an axial tensile load

Explain why it is important to have access to design reference material which is accurate and up to date when working on design proposals. You should make reference to sources of information such as manufacturers’ catalogues, mechanical and physical properties databases and design databases. You must address the following points:

 How can you determine if reference material is accurate?

 What system should a company have in place to ensure that its engineers have

access to reference material which is accurate and wide ranging?

 What are the technical implications if design calculations are flawed because they

are based on incorrect information?

 What are the financial implications for a business if designers use inaccurate

reference material?

Produce a table listing the data sources used for a classroom chair suitable for tall tables. As well as listing the source you should explain what information you obtained and how you used it. You must include sources from the following categories:

 component manufacturers’ catalogues

 materials databases

 design databases