vii PRINCIPLE OF ARCHIMEDES 105 



mercury weigh 49 Ibs. , how many cubic inches of oxygen would con- 

 tain the same quantity of matter as a cubic inch of mercury ? 



17. In a certain state of the atmosphere 100 cubic inches of air 

 weigh .31 grains ; at a temperature the same as that of air 30 cubic 

 inches of mercury weigh 14 '88 Ibs. Find the number of cubic inches 

 of air which contain as much matter as a cubic inch of mercury. 



18. If 28 cubic inches of water weigh a pound, what will be the 

 specific gravity of a substance, 20 cubic inches of which weigh 

 3 Ibs. 



19. The volume of A is 3 cubic feet and its mass is 4 cwt. ; the 

 volume of B is 24 cubic inches and its mass is 35 oz. Find the ratio 

 of the density of A to the density of B. 



20. Describe a method of determining the specific gravity of a 

 liquid. 



21. Describe the method of determining the specific gravity of a 

 body by weighing it alternately in air and water. 



If a body weighs 14 '4 grams in air and 12 grams in water, what 

 is its specific gravity ? 



22. Explain what is rieant by specific gravity. A body of specific 

 gravity 5 weighs 20 gruns in air ; what will the body weigh when 

 immersed in water . 



23. How would you determine the volume of a pebble in cubic 

 centimetres ? 



A number of nails are driven into a rough piece of wood, one 

 cubic centimetre of which weighs 0'5 gram. It is required to find 

 the weight of the nails without pulling them out. How could this 

 be done ? 



24. A covered tin canister having a volume of 88 cubic centi- 

 metres contains just enough shot to sink it to the top of the cover 

 when placed in cold water. Determine from this information 



(a) The weight of the canister and shot. 



(6) The weight of the water displaced by the canister. 



25. Define mass, volume and density, and state the relation that 

 exists between them. 



Suppose you were given two irregular pieces of metal, one of which 

 was gold and the other gilded brass. How would you find out by 

 a physical method which piece was gold ? 



26. Explain why a ship made of iron will float in water, though 

 iron itself is heavier, bulk for bulk, than water ? 



