NATIONAL CERTIFICATE (VOCATIONAL) APPLIED ENGINEERING TECHNOLOGY NQF LEVEL 4 NOVEMBER 2009

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1 NATIONAL CERTIFICATE (VOCATIONAL) APPLIED ENGINEERING TECHNOLOGY NQF LEVEL 4 NOVEMBER 2009 ( ) 30 October (Y-Paper) 13:00 16:00 A non-programmable scientific calculator may be used. This question paper consists of 8 pages.

2 ( ) -2- NC210(E)(O30)V TIME: 3 HOURS MARKS: 100 INSTRUCTIONS AND INFORMATION Answer ALL the questions. Read ALL the questions carefully. Number the answers according to the numbering system used in this question paper. ALL the sketches must be neat, clean and in proportion. g = 9,81 m/s 2. Write neatly and legibly.

3 ( ) -3- NC210(E)(O30)V QUESTION 1: MECHANICAL FUNDAMENTALS OF THE ENGINEERING INDUSTRY 1.1 Name ONE lubricant used to reduce friction between sliding machine parts. 1.2 Explain the difference between Newton s second and third laws of motion. (4) 1.3 Name THREE moving elements of a reciprocating pump. (3) 1.4 Give TWO differences between hydraulic and pneumatic systems. 1.5 A trolley with a mass of 20 kg moves on a horizontal plane. The force of 4N is exerted on the trolley to maintain constant motion. Determine the coefficient of friction between the plane and the trolley. (5) 1.6 State THREE of the most important aspects to take into consideration when applying worksite health and safety practices. (3) 1.7 Name TWO different types of impellers of the centrifugal pump. 1.8 Give THREE reasons for fitting covers on chain drives. (3) 1.9 State TWO advantages of single helical gears.

4 ( ) -4- NC210(E)(O30)V 1.10 Choose a sentence from COLUMN B to match the description in COLUMN A. Write only the letter (A J) next to the question number ( ) in the ANSWER BOOK. COLUMN A COLUMN B Cross-belt drive A regulates the flow of gases Flexible couplings B regulates the flow of liquids Pneumatic valves C are used to support axial loads Hydraulic valves Thrust bearings D the belt is crossed if the drive pulley rotates in the opposite direction to the driven pulley Diverter valves Pinion E are used when the two shafts to be joined are not in a straight line with each other Wheel Evaporator Dynamic seals F G directs the fluid in a system to different components uses the cooling action of the vaporising refrigerant to cool the inside of the fridge H are used where there is relative motion between surfaces I is the small gear J is the larger gear (10 1) (10) [35]

5 ( ) -5- NC210(E)(O30)V QUESTION 2: ENGINEERING PRACTICES USED TO CONSTRUCT PROTOTYPES 2.1 Calculate the reactions of the beam shown in FIGURE 1 below. FIGURE Draw the shear force and bending moment diagrams for the beam shown in FIGURE 1. (6)

6 ( ) -6- NC210(E)(O30)V 2.3 You are given the task to design a prototype frame for a mountain bike. Using the step-by-step chart given below of a typical design process, list ONE example of an action you will take or a question you will ask during each step of the design process of a prototype frame. (Hint: Your design process must consider modern environmental concerns and manufacturing processes) DESIGN SPECIFICATION/PURPOSE DEFINE MANUFACTURING PROCESS OF PROTOTYPE RECORD INFORMATION AND GENERATE INITIAL TESTING OF PROTOTYPE DESIGN IDEAS PREPARE INITIAL DRAWINGS OF DESIGN ANALYSE TEST RESULTS GENERATE ACCURATE PROTOTYPE DIMENSIONS TO SPECIFICATIONS REVIEW DESIGN (10) [20]

7 ( ) -7- NC210(E)(O30)V QUESTION 3: FUNCTIONALLY DEPENDENT MECHANISMS IN PROTOTYPES 3.1 Name the different parts of the hydraulic brake system according to the part numbers ( ) shown as in FIGURE 2 below. FIGURE 2 (9) 3.2 What type of fluid is used in this hydraulic system? Explain TWO purposes of lubricating a gearbox. If the pressure in a hydraulic system is 20kPa and the diameter of the plunger is 0,2 m: Find the area of the plunger Calculate the force exerted by the plunger in Newton (3) (3) Name FIVE basic components of a hydraulic system. Pneumatic cylinders, rotary actuators and air motors provide the force and movement of most pneumatic control systems. Give TWO main sections of a pneumatic system. (5) [25]

8 ( ) -8- NC210(E)(O30)V QUESTION 4: CONTROL SYSTEM IS INCORPORATED INTO A PROTOTYPE OF A TECHNOLOGICAL SOLUTION 4.1 Indicate whether the following statements are TRUE or FALSE. Choose the answer and write only 'true' or 'false' next to the question number ( ) in the ANSWER BOOK Any control system is the execution of at least the following FOUR different basic functions: Sensing or information receiving Information storage Information processing Decision and action Information storage in humans is the memory and in machines is a random access memory (RAM) chip. The scale system is not a closed-loop system because there is feedback by the scale controller. A transducer is a part of the sensor that converts any changes to a measurable quantity. Control systems are classified as either closed-loop or tightly closed-loop. The analogue signal is continuously variable whereas a digital signal varies in steps. Each person in an organisation is required to carry out their duties in an efficient, responsible and safe manner without endangering other people and equipment. A light-dependent resistor or LDR is a light-sensitive resistor. A refrigerated air dryer reduces the water vapour content of compressed air. Line filter helps to keep the line free from dust, water and oil. 4.2 Describe, in your own words, how a servomotor works. (4) 4.3 Describe the following methods in which heat is transferred in a substance: Conduction Convection Radiation [20] TOTAL: 100

UNIT D: MECHANICAL SYSTEMS

1 UNIT D: MECHANICAL SYSTEMS Science 8 2 Section 2.0 AN UNDERSTANDING OF MECHANICAL ADVANTAGE AND WORK HELPS IN DETERMINING THE EFFICIENCY OF MACHINES. 1 3 MACHINES MAKE WORK EASIER Topic 2.1 4 WHAT WOULD