1. SECTION A Answer all parts (a - g) of Question 1 in this section. Each part of this question is worth 4 marks. Allow

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1 Section A Answer All Parts A G Of Question 1 In This Section Each Part Of This Question Is Worth 4 Marks Allow 1 (501.83 KiB) Viewed 34 times

1. SECTION A Answer all parts (a - g) of Question 1 in this section. Each part of this question is worth 4 marks. Allow approximately 52 minutes for this question. (a) In the working stress design methodology, the allowable design stress for an engineering material includes a factor of safety. The purpose of the factor of safety is to ensure that stresses resulting from loading are always kept within the elastic range of the material. Explain why the factor of safety for timber is always significantly higher than the factor of safety for mild steel. (b) A mild steel hanger consists of a 10 mm diameter steel rod. If the allowable tensile stress for the steel rod (ow) is 140 N/mm², what is the maximum mass, in kilograms, that the hanger should be allowed to carry? (c) Answer both parts. (i) Explain, with the aid of a sketch, why thrust blocks are often required on the outer side of a bend in a water supply pipeline. (ii) Why can the water's change in momentum when passing through the bend usually be ignored when calculating the required size of the thrust block? (d) A sharp-edged, rectangular weir controls the volumetric flow rate of water flowing in a water race. Using the equation provided below, determine the maximum allowable still water depth above the crest of the weir if the volumetric flow rate is not to exceed 75 litres/s and the length of the weir is 2.00 m. Q=1.75 LH³/2 (e) Define the term 'impulse-momentum effect' and briefly discuss how this effect is utilised to generate velocity in a 'jet boat'. (f) In open channel flow systems (i.e. systems that are open to the atmosphere), it is important to consider a channel's freeboard when sizing its cross-section. i. Define the term freeboard. ii. State why it is important to consider freeboard when designing an open channel. (g) This sub-question relates to stormwater catchments. i. What three characteristics of a stormwater catchment basin are used to determine its time of concentration? ii. What, together with an intensity-duration-frequency curve, is the time of concentration used to determine? (Total 28 marks) 2 TURN OVER