Page 1 



1919 



Comprehensive Examination 

 PHYSICS 



Friday, June 20 2-5 p.m. 



Answer ten numbered questions, distributed as follows: three from Group I, two from 

 Group n, two from Group IV, two from Group V, and any one of the remaining questions. 



Show clearly the method by which you obtained your answers to problems and state 

 the imits used in each case. 



Attach to the answer in each case the number and letter used in the printed paper. 



Group I 



1. 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. 



a) What weight of water must be let into the tanks just to submerge the 



boat? 



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



required to submerge the boat ? 



c) What is the total force, due to water alone, against the hatch, 3 by 4 ft. 



in size, at a depth of 100 ft. in the ocean ? 



2. A uniform pole, AB, 10 ft. long and weighing 16 lbs., has a 10-lb. weight 



attached 4 ft. from the end A. The pole is carried by two men, one at the 

 end B and the other 2 ft. from the end A. 



a) How much does each man carry when the pole is held in a horizontal 



position ? 



b) What difference would it make if the end B were more elevated than the 



end A ? 



3. A bicycle tire contains 120 cu. in. of air at a pressure of 20 lbs. per square 



inch. How many strokes must be made on a pump whose cylinder has a 

 volume of 5 cu. in. to increase the pressure in the tire to 30 lbs. per square 

 inch ? Consider the atmosphere as having a pressure of 15 lbs. per square 

 inch and the volume of the tire and the temperature of the contained air 

 to remain constant. 



4. a) How long must a force of 2 lbs. act upon a mass of 10 lbs. to give it a 



velocity of 20 ft. per second ? 

 b) How much work will the force do in the time involved ? 



5. What is the force of the backward thrust of the propeller of an airplane 



driven by an engine developing 150 horse-power, when the airplane is 

 traveling 120 miles per hour? 



(THIS EXAMINATION IS CONTINUED ON PAGE 2) 

 ^34 



