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1919 

 PHYSICS 



Friday, June 20 2 p.m. Two hours 



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

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

 in which each answer is expressed. 



Group I 

 (Omit one question from this group.) 



1. A receiver contains 500 cubic centimeters of air under a pressure of 75 centi- 



meters of mercury. What will be the pressure of the air if its volume is 

 reduced to 200 cubic centimeters, the temperature remaining unchanged ? 



2. (a) State Pascal's principle. 



(b) A submarine weighs 1800 tons when its submerging tanks are empty, 



and in that condition 10 per cent by volume of the submarine is above 

 water. What weight of water must be let into the tanks just to sub- 

 merge the boat ? 



(c) If the specific gravity of sea-water is 1.03, what volume of water is 



required to submerge the boat ? 



3. (a) Explain the meaning of these terms: moment of force; acceleration; 



a unit of force. 



(b) Show how to find by a graphical method the resultant of two forces 

 acting at an angle to each other. 



4. A uniform plank 20 feet long, weighing 200 pounds, rests on a flat roof with 



8 feet of its length projecting beyond the edge of the roof. If a keg of 

 nails weighing 50 pounds rests over a point 1 ft. from the inner end, how 

 far out on the plank beyond the edge of the roof may a man weighing 

 180 pounds go without tipping the plank ? 



Group II 

 (Omit one question from this group.) 



5. {a) State the physical difference between a noise and a musical sound. 



[b] Describe briefly an experiment that demonstrates which characteristic 



of a musical sound determines its pitch. 



(c) If the expansion of an organ pipe is ignored, what change, if any, is pro- 



duced in the sound of the pipe by a rise in temperature ? Give reason 

 for your answer. 



6. Describe some common form of resonator and explain resonance as illus- 



trated by its action. 



(THIS EXAMINATION IS CONTINUED ON PAGE 2) 



