(a) Explains why the draught of a ship decreases when it passes from fresh water to seawater and vice versa. (6)

(b) A bulkhead 9 m deep is supported by vertical stiffeners 750 mm apart. The bulkhead is flooded to the top edge with sea water on one side only. Calculate: (10)

(i) shearing force at top

(ii) shearing force at bottom

(iii) position of zero shear.