Q7. (a) State TWO of the MINOR components of the residuary resistance. (2)
(b) A ship has a length of 140 m and floats in sea water of density 1025 kg/3. A geometrically similar model of this ship has a length of 5 m and a wetted surface area of 5.8 m2. The model has a total resistance of 29.55 N when towed in fresh water of density 1000 kg/m3 at a speed corresponding to 15 knots for the ship. Calculate EACH of the following:
(i) the ratio of residuary resistance to total resistance for the model at the corresponding speed; (6)
(ii) the ratio of residuary resistance to total resistance for the ship. (6)
(c) State why the TWO ratios calculated in Q7(b) should be different. (2)
Note: The frictional coefficient the model in fresh water is 1.694
The frictional coefficient for the ship in sea water is 1.415
Speed in rms with the speed index (n) for ship and model 1.825
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