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Q6. A. What do you understand by reserve buoyancy what will happen if the lost buoyancy is greater than the reserve buoyancy.

B. A ship of 8100 tonne displacement floats upright in seawater. KG = 7.5m and GM = 0.45m A tank, whose centre of gravity is 0.5m above the keel and 4m from the centreline, contains 100 tonne of water ballast neglecting free face effect, calculate the angle of heel when the ballast is pumped out.

Q7. A) State briefly, the meaning of the expressions ‘star-connected’ as applied to three-phase a.c. practice. What is the ratio of the maximum line voltage to the maximum phase voltage in each case. (6)

B) Determine the line current taken by a 440V, three-phase, star-connected motor having an output of 45kW at 0.88(lagging) power factor and an efficiency of 93 per cent. (10)

7.a) Explain the term Angle of loll and state the dangers it poses to a vessel. What action to be taken to correct angle of loll. (6)

b. A ship of 22000 tonne displacement is 160 m long and MCTI cm 280tonne m, waterplane area 3060 m2 centre of buoyancy 1 m aft of midships and centre of flotation 4 m aft of midships. It floats in water of 1.007 t/ m3 at draughts of 8.15 m forward and 8.75 m aft.

Calculate the new draughts if the vessel moves into sea water of 1.026 t/ m2

Calculate the metacentric height of the vessel. (10)

8. When a ship is 800 nautical miles from port its speed is reduced by 20%, thereby reducing the daily fuel consumption by 42 tonne and arriving in port with 50 tonne on board. If the fuel consumption in t/h is given by the expression (0.136+0.001 V3) where V is the speed in knots, estimate:(i) The reduced consumption per day; (ii) The amount of fuel on board when the speed was reduced(iii) The percentage decrease in consumption for the latter part of the voyage;(iv) The percentage increases in time for this latter period.

Q9. a) Explain how drooping characteristics cater for stable operation when running in parallel. (6)

b) Two shunt generators X and Y work in parallel. Their external characteristics may be assumed to be a linear over their normal working range the terminal voltage of X falls 265V on no load 230V when delivering 350Ato the busbars, while the voltage of Y falls from 270 V on no load to 240V when delivering 400A to the bus bars. Calculate the current with each machine delivers when they share a common load of 500A. what is thw bus bar voltage under this condition and the power delivered by each machine

Q9. a) Explain why the rudder angle does not normally exceed 35°. (6)

b) A ship of 12000 tonne displacement has a rudder 15m2 in area, whose centre is 5 m below the waterline.  The metacentric height of the ship is 0.3m and the centre of buoyancy is 3.3m below the waterline.  When travelling at 20 knots the rudder is turned through 30 .  Find the initial angle of heel if the force Fn perpendicular to the plane of the rudder is given by: Fa=577 Av2 sin  N, Allow 20% for the race effect. (10)

Q10. A ship of 14000 tonne displacement is 125 m long and floats at draughts of 7.9 m forward and 8.5 m aft. The TPC is 19, GML 120 m and LCF 3 m forward of midships. It is required to bring the vessel to an even keel draught of 8.5m. Calculate the mass which should be added and the distance of the distance of the centre of the mass from midships. (16)

Q9. (a) With aid of a simple sketch, show the normal positions of centre of gravity of a stable ship relative to keel, centre of buoyancy and meta centre. (6)

(b) A ship has 300 t of cargo in the hold, 24 m forward of the midships. The displacement of the vessel is 6000 t and its centre of gravity is 1.2 m forward of midships. Find the new position of the centre of gravity if this cargo is moved to an after hold, 40 m from midships. (10)

Q8. A bilge holding tank of 5 m length, 3 m width and 1.8 m depth has water of density 1.020 t/m3 upto a sounding of 1.3 m and oil of density 0.86 t/m3 is floating on top of water upto an ullage of 0.3 m. Calculate the mass of water and oil in the tank (16)

Q8. a) Explain clearly the meaning of the term "reserve buoyancy". (6)

b) The centre of gravity of a ship of 5000 tonne displacement is 6 m above the keel and 1.5 m forward of midships. Calculate the new position of the centre of gravity if 500 tonne of cargo are placed in the t’ween decks 10 m above the keel and 36 m aft of midships. (10)

Q7. A moving-coil instrument has a resistance of 10 Ω and requires a current of 15 mA to give full- scale deflection. Calculate the resistance value of the resistor necessary to enable it to be used to measure

a) currents up 25A

b) voltages up to 500V. (16)

Q5. A 4-pole lap wound DC shunt generator has an open e.m.f of 250V when the flux per pole is 0.08 Wb and the speed is 10 rev/sec. The speed of the generator is reduced to 10 per cent and the flux per pole is increased by 5% when the generator supplies a load of 100A. Determine the terminal voltage, if the armature resistance is 0.06 ohms and the new total field circuit resistance is 200 ohm. (16)