6. a) (7) A hollow sphere of glass weighs 500 gm. in air and requires a force of 

 1,000 gm. to hold it under water. If the density of the glass is 2.5 

 gm. per cu. cm., what is the volume of the space inside ? 

 b) (3) Is it harder to lift a stone in air than when it is under water ? Why ? 



Group II 



6. (10) An automobile tire contains 1,500 cu. in. of air at 12° C. and a pressure 



of 90 lbs. per sq. in. Driving the car causes the air in the tire to be 

 heated to 33° C. What is the pressure, assuming the air in the tire 

 to have now a volume of 1,530 cu. in. ? 



7. a) (4) Describe the processes by which heat passes from the steam in a steam 



radiator to the objects in the room. 

 b) (6) Steam at 100° C. is passed into a 55-kg. iron radiator. Calculate 

 the weight of steam condensed in heating the radiator from 5° C. 

 to 100° C. (Specific heat of iron =0. 11.) 



8. a) (4) Describe a laboratory experiment to determine the latent heat of 



vaporization of water, 



b) (4) What quantities must be determined and how would you use these in 



calculating the result ? 



c) (2) Mention two important sources of error which must be guarded 



against. 



Group III 



9. a) (5) Name and define three characteristics by which different sounds are 



distinguished from each other. 

 b) (5) Explain how each of these characteristics may be altered in the case 

 of a vibrating string. 



Group IV 



10. a) (4) Show how the intensity of a source of light may be measured. 



b) (1) What is the unit of intensity of light ? 



c) (5) If a light 6 ft. away is illuminating your book, how far away 



should a light 16 times as bright be placed to produce the same 

 illumination ? 



11. At what distance from a double convex lens of focal length 12 in. must an 



object be placed to cause a real image: 



a) (4) of twice the length of the object ? 



b) (3) of half the length of the object? 



c) (3) of the same length as the object ? 



12. a) (3) What is a spectrum and how is it produced ? 



b) (2) What are the Fraunhofer lines in the solar spectrum ? 



c) (2) What do these lines indicate ? 



d) (3) Explain the appearance of each color in the American flag when placed 



in pure blue light; when placed in pure red light. 



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