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1920 

 PHYSICS 



Monday, September 20 2-5 p.m. 



Answer ten questions as indicated below. No extra credit will be given for more 

 than ten questions. Indicate clearly your reasoning in each problem and state the units 

 in which each answer is expressed. 



Number and letter each answer to correspond with the question selected. 



Group I 

 {Oviit one question from this group.) 



1. Describe the construction and explain the operation of the piston air pump: 

 c) As employed for exhausting a receiver. 



h) As employed for compressing air. 



2. The density of a piece of metal is 165 pounds per cubic foot. 



a) What is its specific gravity ? 



h) What will a cubic centimeter of the metal weigh ? 



c) How much will a cubic foot of the metal weigh when immersed in alcohol 

 of specific gravity 0.8 ? 



3. A hill rises 50 feet in its length of 2,000 feet. What horse-power is needed to 



draw a load of 5 tons at a uniform rate up the hill in 10 minutes if 20 per 

 cent of the total work is done against friction ? 



4. a) A boy weighing 50 pounds is seated in a swing supported by two parallel 



ropes 13 feet long. How great a horizontal force will be required to hold 

 him 5 feet to one side of the vertical position ? 



b) What will be the tension then on each of the swing ropes ? 



Group II 

 {Omit one question from this group.) 



5. Given a tuning-fork making 256 vibrations per second, how could you deter- 



mine the velocity of sound by means of a resonating column of air ? 



6. a) How would the intensity of the sound of a bell heard by a man 1,000 feet 



away compare with the intensity of the sound heard by a man 2,500 feet 

 away? 

 b) If the tone of a man's voice has a frequency of 100, how long are the waves 

 which are produced when he speaks in air at a temperature of 20° C. ? 



Group III 

 {Omit one question from this group.) 



7. a) How does change of pressure aflfect the melting-point of ice or the freezing- 



point of water ? 



b) How do the boiling-point and the freezing-point of salt water differ from 



those of pure water ? 



c) How is the boiling-point of water affected by change of pressure ? 



(THIS EXAMINATION IS CONTINUED ON PAGE 2) 



