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Q2. A crankcase relief door is 240 mm diameter and has a mass of 0.6 kg. The door operates along a horizontal axis and is kept closed by a helical spring made from 8 mm diameter wire. The spring has six coils of mean diameter 60 mm and is compressed by 18 mm on assembly.

Calculate EACH of the following:

(a) the minimum gas pressure in the crankcase that will cause the door to open;

(b) the time taken for the door to open 60 mm, assuming an effective pressure of 0.3 bar above atmospheric pressure acts on the door throughout the opening period.

Note: Modulus of Rigidity for spring material = 70 GN/m²