AET Level 4 example exam paper (2012)

QUESTION 1

1.1

Friction can be very handy in everyday life. List FIVE situations where it is advantageous to have friction in the engineering related environment.

(5)

1.2

If machining is an example of a finishing process, name FOUR other finishing processes.

(4)

1.3

State the following Newton’s law’s of motion and give an application of each.

	1.3.1	First law of motion.	(3)
	1.3.2	Second law of motion.	(3)
	1.3.3	Third law of motion.	(3)

1.4

Give TWO functions of a lubricant.

(2)

1.5	A truck with a mass of 3.5 ton moves on a horizontal highway.   A force of 7.8 kN is exerted on the truck to maintain constant velocity. Determine the coefficient of friction between the wheels and the road.	(6)
		[26]

QUESTION 2

2.1

Choose a description from COLUMN B that matches a/an word/item in COLUMN A.   Write only the letter (A – H) next to the question number (3.1.1 – 3.1.5) in the ANSWER BOOK.

2.1.1 2.1.2 2.1.3 2.1.4 2.1.5

COLUMN A Pressure relief valve Universal coupling Open belt drive Footstep bearing Diaphragm pump

A B C D E F G H

COLUMN B Support shafts which revolve horizontally. Is used where pulleys have to rotate in opposite directions. Connects shafts whose axes are at an angel other than 180 degree. Support shafts which revolve in a vertical position. Use a flexible member to displace fluid. Is designed to open at a predetermined pressure to allow the hydraulic fluid to bypass the system safely until normal working pressure is restored. Is used where both pulleys have to rotate in the same direction. A flexible diaphragm operating as a valve.

(5)

2.2

Give TWO examples of what causes vibration of a machine’s moving parts.

(2)

2.3

List SEVEN causes of failure relevant to a motor vehicle’s hydraulic system that needs to be checked at regular intervals.

(7)

2.4	The liquid pressure in a cylinder with a diameter of 150 mm is 3.7 kPa.   Calculate the force on the piston rod when the piston moves backwards.	(6)
		[20]

QUESTION 3

3.1

A horizontal beam is 3m long and is supported at the left-hand end and also 2,5m from the left-hand end. The beam carries the following point loads (ignoring the mass of the beam): 300N – 1m from the left end 400N – 2m from the left end 200N – at the right end

3.1.1

Make a neat sketch of the beam with all the relevant information on it.

(7)

3.1.2

Calculate the reactions.

(10)

3.1.3

Check by means of the calculation whether the forces are in equilibrium to each other.

(3)

[20]

QUESTION 4

4.1

You are given the task of designing a prototype for a skateboard (wheels and axles are supplied).   Using the step-by-step diagram (given below) of a typical design process, list at least ONE example of a step you will take, or a question you will ask during the design of the prototype frame for the skateboard. Hint: Your design process must consider modern environmental concerns and manufacturing processes.) 4.1.1 Design specifications/ purpose 4.1.2 Record information and generate initial design ideas 4.1.3 Prepare initial drawings of design 4.1.6 Testing of prototype 4.1.5 Define manufacturing processes of prototype 4.1.4 Generate accurate prototype dimensions to specification 4.1.7 Analyse test results 4.1.8 Review design

(10)

4.2

Describe the following methods in which heat is transferred in a body:

	4.2.1	Conduction	(2)
	4.2.2	Convection	(2)
	4.2.3	Radiation	(2)
			[16]

QUESTION 5

5.1

What is the difference between analogue and digital signals?   Explain with the aid of a sketch.

(5)

5.2

Two different methods of controlling a conveyor are shown in the diagram FIGURE 3.   In the one system a timer is used and in the other system a scale is used. In each case it is required to fill the truck with a set amount of sand.  Once full the truck makes way for another truck. In the one method the timer, which controls the motor, is set for a certain period and provided that there is a constant supply of sand the truck is filled.   In the other method, the scale turns on the motor until the correct amount of sand is placed in the truck, and then switches the motor off. What kind of control systems are used in each case?   Explain your answer. FIGURE 3

(5)

5.3

Each person in an organization is required to carry out his/her duties in an efficient, responsible and safe manner without endangering other people and equipment. List EIGHT responsibilities of a process operator when working with mechanical equipment.

(8)

[18]

TOTAL

100