Mar. 5.] THE NEW ZEALAND GAZETTE. 499

2. The high-pressure cylinder of a triple-expansion engine is 24 in. diameter and the length of the stroke 4 ft., the length of the connecting-rod being four times that of the crank. The boiler-pressure is 180 lb. per square inch, and the back pressure on the high-pressure piston 75 lb. per square inch, and steam is cut off at three-quarters of the stroke. Find, neglecting inertia forces, the maximum pressure per square inch on the crank-pin bearing which is 12 in. long, the diameter of the crank-pin being 12 in.

3. A vessel of 10,000 tons displacement travels at a speed of 15 knots. What is the horse-power of the engines if the total resistance to the vessel’s motion is 0·003 of the displacement and the propulsive efficiency 60 per cent.?

4. A block of ice weighing 20 lb. is melted in an open vessel, and heat is supplied until half of the melted ice has been evaporated. If the temperature of the ice when placed in the vessel was 28 degrees Fahrenheit, find the total heat in British thermal units supplied.

5. A steel ingot weighing 1 cwt. is drawn along a level track at uniform speed by means of a rope which is inclined at an angle of 30 degrees to the track. If the pull in the rope is 16 lb., what is the co-efficient of friction?

6. A rectangular block of wood weighing 10 lb. floats in fresh water. A piece of iron sufficiently heavy to bring the upper surface of the block to the water-level is placed on top of it. Find the specific gravity of the wood if the weight of the iron is 3 lb.

Second Paper.

The following three questions are for both Ordinary and Motor Examination:—

7. A vessel of 1,000 tons displacement when proceeding to a berth in dock moves at a speed of 1½ knots after the engines have been stopped. If the vessel is brought to rest in 30 seconds by means of a mooring-rope, find, neglecting all frictional resistances, the average pull in the rope.

8. The strength of the current passing through an electric heater is 5 amperes and the difference of potential at the terminals 200 volts. Find the amount of heat in British thermal units given out by the heater per hour.

9. A cylindrical tank 3 ft. diameter and 8 ft. long floats horizontally in water. If the area of the water-plane is 16 square feet, what is the draught of the tank?

The following three questions are for Ordinary Examination only:—

10. The length of the combustion-chamber of a marine boiler is 3 ft. 4 in. at top, and the thickness of the tube plate 0·75 in. The external diameter of the tubes is 3¼ in., the thickness of the plain tubes 0·125 in., and the horizontal pitch 5 in. Allowing a compressive stress in the material of 14,000 lb. per square inch, find the maximum working-pressure for which the tube plate is suitable.

11. Steam is admitted to the cylinder of an engine at 150 lb. per square inch (gauge), and release takes place at 0·9 of the stroke. The clearance volume is 0·1 of the volume swept by the piston and the pressure of the steam 50 lb. per square inch (gauge) when exhaust begins. Assuming isothermal expansion, find the point of the stroke at which cut-off takes place.

12. A cylindrical tank 3 ft. diameter and 8 ft. long floats horizontally in water. If the area of the water-plane is 16 square feet, what is the draught of the tank?

The following three questions are for Motor Examination only:—

13. A Diesel engine of 1,000 indicated horse-power consumes 340 lb. of fuel per hour. Find the thermal efficiency of the engine if the calorific value of the fuel is 19,000 British thermal units per pound.

14. An air-receiver contains 50 lb. of air at 50 lb. per square inch (gauge) and 60 degrees Fahrenheit. Owing to the occurrence of fire in the vicinity of the receiver 1,000 additional British thermal units are imparted to the air. Assuming that there is no escape of air from the vessel, find the pressure of the air after the additional heat has been imparted to it. (NOTE.—The specific heat of the air is 0·17.)