DieselShip's Online Content Library

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)

Q7. (a) Explain why the draught of a ship decreases when it passes from fresh water to seawater and vice versa. (6)

(b) A lock gate which is 15m wide has salt water on one side to a depth of 8m and fresh water on the other side to a depth of 9m. Find the resultant thrust on the lock gate and state on which side of the gate it acts. (10)

Q9. A piece of aluminium has a mass of 300 g and its volume is 42 cm3

Calculate

a) its density in kg/m3

b) the relative density

c) the mass of 100 cm3 of aluminium (16)

Q7. a) Define TPC. Explain why TPC for a given draught will vary with the density of the water in which the ship floats? (6)

b) The pitch of a propeller is measured by means of a batten and cord. The horizontal ordinate is found to be 40 cm while the vertical ordinate 1.15 m at a distance of 2.6 m from the centre of the boss. Calculate the pitch of the propeller and the blade width at that point. (10)

Q6. The open-circuit voltage of a cell as measured by a voltmeter of 100 Ω resistance, was 1.5V, and the p.d. when supplying current to a 10 Ω resistance was 1.25V, measured by the same voltmeter. Determine the e.m.f. and internal resistance of the cell. (16)

Q4. a) Sketch and describe a star-delta starter for starting an induction motor (10)

b) Three similar coils, each having a resistance of 10 ohms and an inductance of 0.02 H are connected in

i) Star

ii) Delta to a 3-phase, 50-Hz supply with 500V

Calculate the total power absorbed and the line current in each case. (6)

Q9. (a) Explain about non-linear resistors with some examples and illustration on how they differ from linear resistor. (6)

(b) A half-wave rectifier is used to supply 50V d.c. to a resistive load of 800Ω. The diode has a resistance of 25 Ω. Calculate a.c. voltage required. (10)

Q7. (a) Define Density, Relative Density (6)

(b) A bilge holding tank of 5 m length, 3 m width and 1.8 m depth has water of density 1.020 t/m3 up to a sounding of 1.3 m and oil of density 0.86 t/ m3 is floating on top of water up to an ullage of 0.3 m. Calculate the mass of water and oil in the tank. (10)

Q8. (a) Derive the formula for Admiralty Coefficient. (6)

(b) A ship travels 900 nautical miles at a speed of 12.5 knots and burns 150t of fuel over the voyage. Estimate the distance the ship could travel at a speed of 13.5 knots on 250t of fuel. (10)

Q4. a) What is a commutator? Discuss its rectifying action in detail. (6)
(b) Determine the line current taken by a 440 V, three-phase, star-connected motor having an output of 45 Kw at 0.88 (lagging) power factor and an efficiency of 93 per cent. (10)

Q6. a) What is back emf? Derive the relation for the back emf and the supplied voltage in terms of armature reactance. (6)

b) Two earth lamps at 120 V, 15 W are used on a 110 V distribution circuit. Due to damage to a motor, the resistance of the positive line is reduced to 10 ohm and that of the negative line to 5 ohm. Find the voltage across each lamp and the extra load on the generator due to the fault. (10)