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Example 4 (SPM 2007; Question 11) Diagram 4.1 shows four tankers, P, Q, R and S, with different specifications. You are required to determine the most suitable tanker to deliver oil safely. Study the specifications of all the four tankers from the following aspects:

- the type of brakes - the number of tyres - the number and size of the tanks - the distance between the trailer and the tractor.

Explain the suitability of the aspects. [10 marks]

Diagram 4.1

Section C

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SUGGESTED ANSWER:

Specifications Reasons ABS is more effective brake

In ABS, all tyres will be stopped once the brake is applied. This will ensure the tanker to stop immediately.

Two tyres is better option

It provides better support to the tanker. In case one tyre explodes, the stability of the tanker is not greatly affected because its base area is still large.

Five small tanks is better option

The small tanks with distributed mass will have smaller inertia. This can reduce the inertial impact if the tanker stops suddenly.

Use tanker in which there is a distance between trailer and tractor

This ensure that trailer will not collide with the tractor, if the trailer is still moving when the tractor has stopped moving.

Tanker R is the most suitable tanker to deliver oil safely. This is because it has ABS brake, a set of two tyres, five small tanks and a distance between trailer and tractor.

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Example 5 (SPM 2009; Question 12) You are asked to investigate the design and the characteristics of five filament lamps shown in Diagram 5.1. Explain the suitability of each characteristic of the lamps and determine the lamp which can produce the brightest light. [10 marks]

Diagram 5.1

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SUGGESTED ANSWER:

Specifications Reasons Tungsten wire is used

It has high melting point

The wire is thin So that the resistance is high The wire is coiled So that the resistance is high The bulb is filled with nitrogen gas at high pressure

To reduce the vaporization of metal at high temperature

Bulb P is the lamp which can produce the brightest light. This is because it uses tungsten wire with thin and coiled wire and the bulb is filled with nitrogen gas at high pressure.