Question 6
a. If the contact angle of a liquid with its container walls is 90°what can we say about the different forces involved and what arethose forces? Include a discussion of the meniscus in this case. [3marks]
b. Explain why the pressure inside a bubble is larger than thepressure surrounding the bubble. [2 marks]
c. At the top of a ski lift a 1 tonne concrete block counterweightis supported by a 10 m long steel cable (of 16 mm diameter when notunder stress). You must include the mass of the cable whenanswering the following questions. The density of steel is 8000 kgm-3, the tensile strength of steel is 5.0 x 108 Pa, the ElasticModulus of steel is 2.1 x 1011 Pa and Poisson’s ratio for steel is0.28.
i. What is the safety factor of the system? Comment on your answer.[6 marks]
ii. What is the change in diameter of the cable when supporting thecounterweight? [3 marks]
iii. What energy is stored in the cable when supporting thecounterweight? [2 marks]
iv. Calculate the Bulk and Shear moduli of steel. [4 marks]
