Question

a) i. Explain the difference between elastic and plastic behaviour. [2 marks] ii. Explain how stretching an object gives rise to internal shear. [3 marks] iii. What is meant when a material is described as having non-isotropic properties? [1 mark]

b) Water circulates throughout a house in a hot water heating system. The water is pumped at a speed of 0.50 ms–1 through a 4.0 cm diameter pipe in the basement at a pressure of 3.0 x 105 Pa. What will the flow speed and pressure be in a 2.6 cm diameter pipe on the second floor 5.0 m above the pump? [4 marks]
c) Engine oil passes through a fine 1.8 mm diameter tube in a prototype engine. The tube is 5.5 cm long. Assuming that the oil has a viscosity of 0.2 Nm–1 at the engine operating temperature what pressure difference is needed to maintain a flow rate of 5.6 x 10–6 m3 per minute? [3 marks]
d) A factory makes spaghetti with an extremely small hole down the centre of only 10–4 m radius. As the spaghetti is lowered vertically into the near boiling water (surface tension = 0.059 N m–1, density = 103 kg m–3) how far up the spaghetti above the external water line would the water be drawn if the contact angle is 45°. [2 marks]
e) i. Calculate the surface tension of water if the pressure in submerged air bubbles of radius 1 cm is 150,315 Pa at a depth of 5 m. Assume that atmospheric pressure is 101300 Pa and water has a density of 1000 kg m-3. [4 marks]

ii. Assuming there are 1000 such bubbles how much energy was required to form these bubbles?   

Answer 1