JANUARY 2013 CONFIDENTIAL

SECTION A (Total: 60 marks)

INSTRUCTION: Answer ALL questions.

Please use the answer booklet provided.

Question 1

(a) Equation p + a v2 = b is dimensionally correct. Unknown p and v represent pressure

and velocity respectively. Derive the dimensional analysis and determine S.I unit of

a.

(6 marks)

(b) The velocity time graph is shown below in Figure 1 for an object travelling from one

point to another point within 8 seconds. Determine the accelerations at point A, B

and C. Then estimate the distance covered in 8 seconds.

Figure 1: Velocity Time Graph

(14 marks)

LGD10703 ENGINEERING SCIENCE 1

JANUARY 2013 CONFIDENTIAL

Question 2

(a) State the theory of Newton’s Law and formulae with an example each of them;

i. Newton’s First Law

ii. Newton’s Second Law

(6 marks)

(b)

Figure 2: Cable with pulley

A 7.5 kg object is placed on a frictionless horizontal table which is connected to a

cable that passes over a pulley and then is fastened to a hanging 12.5 kg object, as

in Figure 2.

i. Draw free-body diagrams of both objects.

ii. Analyse the acceleration of the two objects and the tension in the string.

(14 marks)

LGD10703 ENGINEERING SCIENCE 2

JANUARY 2013 CONFIDENTIAL

Question 3

(a) Potential energy and kinetic energy are two forms of energy classified under the

Mechanical energy. Explain briefly their definitions with the aid of relevant formulae.

(6 marks)

(b) A particle of mass m = 0.5 kg is released from point A and slides on the frictionless

track shown in Figure 3. Evaluate;

i. the particle's speed at points B and C.

ii. the net work done by the gravitational force in moving the particle from A to C.

Figure 3: Frictionless track

(14 marks)

LGD10703 ENGINEERING SCIENCE 3

JANUARY 2013 CONFIDENTIAL

SECTION B (Total: 40 marks)

INSTRUCTION: Answer only TWO questions.

Please use the answer booklet provided.

Question 4

(a) State two Pascal’s principle.

(4 marks)

(b) A hydraulic lift is used to jack a 970-kg car 120 mm off the floor. The diameter of the

output piston is 180 mm, and the input force is 500 N shown in Figure 4. Determine;

i. Area of the input piston.

ii. Work done in lifting the car 120 mm.

iii. If the input piston moves 150 mm in each stroke, determine the height the

car move up for each stroke?

Figure 4: Hydraulic Jack

(12 marks)

(c) Draw a simple barometer and determine its standard Pressure in atmosphere.

[Hint: ρmercury=13.6 x 103 kg/m3 , g = 9.81ms-2].

(4 marks)

LGD10703 ENGINEERING SCIENCE 4

JANUARY 2013 CONFIDENTIAL

Question 5

(a) Explain with sketch the relationship between pressure (P), volume (V) and

temperature (T) of an ideal gas law;

i. Boyle’s Law.

ii. Charles’s Law.

iii. Gay-Lussac’s Law.

(6 marks)

(b) A vertical cylinder of cross-sectional area A is fitted with a tight-fitting, frictionless

piston of mass m shown in Figure 5;

i. If n moles of an ideal gas are in the cylinder at a temperature of T, determine the

height h at which the piston is in equilibrium under its own weight?

ii. Determine the value for h if n = 0.200 mol, T = 400 K, A = 0.008 00 m2, and

m = 20.0 kg.

(8 marks)

Figure 5: Frictionless Piston

(c) If 18.75 mol of helium gas is at 10.0°C and a gauge pressure of 0.350 atm. Analyse;

i. the volume of the helium gas under these conditions.

ii. the temperature if the gas is compressed to precisely half the volume at a gauge

pressure of 1.00 atm.[Hint: R=8.314J/(mol.K), P=1.013 x 105 N/m2]

(6 marks)

LGD10703 ENGINEERING SCIENCE 5

JANUARY 2013 CONFIDENTIAL

Question 6

(a) With the aid of neat sketch, explain briefly the first law of thermodynamics.

(6 marks)

(b) Consider the following two-step process. Heat is allowed to flow out of an ideal gas at

constant volume so that its pressure drops from 2.2 atm to 1.4 atm. Then the gas

expands at constant pressure, from a volume of 6.8 L to 9.3 L, where the

temperature reaches its original value shown in Figure 6. Analyse;

Figure 6: Two-step process

i. the total work done by the gas in the process.

ii. the change in internal energy of the gas in the process.

iii. the total heat flow into or out of the gas.

(12 marks)

(c) List two applications of thermodynamics.

(2 mark)

END OF QUESTION

LGD10703 ENGINEERING SCIENCE 6

JANUARY 2013 CONFIDENTIAL

Formulae

i)v=u+at

ii )s=ut+12at 2

iii )v2=u2+2as

iv )K . E=12mv2

v )P . E=mghvi)Components :Parallel−mg sinθPerpendicular−mgcos θvii) Ideal−gas−LawPV=nRTviii)Trigonometry

a )sinθ= y / zb )cosθ=x /zc ) tanθ= y / x

Constant

i)Gravitional , g=9.81ms−2

ii)Gas ,R=8 .314 J /mol .Kiii )STP(T=273K ,P=1.0atm=1.013×105Nm−2=101 .3kPa )iv)Avogadro ' s , N A=6 .02×10

23/mol

LGD10703 ENGINEERING SCIENCE 7

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