Engineering Science N2 august 2012 memo

Engineering Science N2

ENGINEERING SCIENCE N2 QUESTION PAPER

AUGUST 2012

Here are the answers to this question paper:

Question 1

1.1        27,5 m/s = 99 km/h

1.2        graph

1.2.1             a = 5,5 m/s^2

1.2.2             s  = 68,75 m

1.2.3             s in 20 s = 11 m 

1.4                Distance = 150 m

1.4.1             Displacement = 111,803 m

                     Direction = S 71,565 degrees E or 71,565 deg E of S

Question 2

2.1               The Resultant of a system of forces is that single force that can replace the system of forces, and produce the same result as the system of forces.

2.2               Beam

2.2.1            F = 12,5 kN

2.2.2            L = 17,5 kN

2.3               F = 69,738 N

2.4               Turning point is in the centre, 0,75 m from either end.

Question 3  

3.1 Potential Energy is the energy a body possesses due to its mass and height above a reference plane.

3.2

3.2.1    t = 2,041 s

3.2.2    PE at highest point = 3257,99 J

3.2.3    Velocity at ground level = 32,954 m/s

3.2.4     Momentum at ground level = 197,724 kg-m/s

Question 4

4.1    Power is the rate at which work is being done.

4.2

4.2.1  Graph

4.2.2  Total weight of cable = 5250 N

4.2.3  Work done = 1 841 875 J or 1,841875 MJ

4.2.4 Power = 106 kW

Question 5

5.1  Belt drives have the following advantages over gear drives:

• Lubrication requirements are simplistic, as only the pulley bearings need to be greased.
• Power can be transmitted with shafts at large centre distance apart.
• Belts are cheaper to maintain and/or replace than gears.

5.2    

5.2.1    Actual load = 4050 N

5.2.2    Displacement Ration (Velocity Ratio) = 48

5.2.3      

5.3      

5.3.1    Effective force = 440 N

5.3.2    Power = 3 455,752

5.4 Sketch of differential wheel-and-axle

Question 6 

6.1

6.1.1 depth = 81,633 m

6.1.2 Pabs  = 921,3 kPa

6.2 

6.2.1     false

6.2.2     true

6.3   

6.3.1   W para = 920,164 N

6.3.2   W perp  = 1730,577 N

6.3.3    Friction force = 920,164 N

6.3.4    Coefficient of friction = 0,532

Question 7: Heat

7.1            When 1 kg of the coal is combusted, 30 MJ of heat energy will be released.

7.2

7.2.1        Heat per hour = 270 MJ

7.2.2        final temp of water = 90,233 deg celsius

7.3           final temp = 73,824 deg celsius

7.4           An increase in pressure increases boiling point, and vice versa.

Question 8

8.1

8.1.1      A molecule is a chemical combination of two or more atoms, from the same or of different elements.

8.1.2     An ion is an atom which has either lost or gained electrons.

8.2   electrons - negative

         protons - positive

         neutrons - neutral

8.3    Electroplating is used to :

• beautify a plain metal (such as mild steel) with a shiny coating of an expensive metal, such as silver or gold
• protect metals againt rust