Pagel 



1920 



Comprehensive Examination 



PHYSICS 



Friday, June 25 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 

 (Omit one question from this group) 



1. a) Explain the principle of the mercury barometer. 



b) What is the pressure in the mercury halfway up the barometer column ? 



c) What effect does the diameter of the barometer tube have upon the height 



of the mercury column ? 



2. a) State Archimedes' principle. 



b) What application, if any, does this principle have in aeronautics ? 



c) Since hydrogen is lighter than air, would pumping more and more hydrogen 



into a balloon increase its lifting power ? Explain fully. 



3. A truck weighing 4 tons changes its speed at a uniform rate from 10 miles 



per hour to 20 miles per hour in 2 minutes. 



a) What force is required to produce this change in speed ? 



b) What distance does the truck go in the 2 minutes ? 



4. A cord 10 feet long has its ends fastened 8 feet apart on a ceiling and supports 



a weight of 20 pounds from its middle point. Find the tension in the cord. 



Group II 

 (Omit one question from this group) 



5. a) When musical instruments are not in exact imison one hears a throbbing 



called "beats." Explain. 

 b) What is meant by resonance ? 



6. a) Describe a method for determining the velocity of sound in air. 



b) An open organ pipe is 3.5 feet long. What is the frequency of its funda- 

 mental tone ? 



(THIS EXAMINATION IS CONTINUED ON PAGE 2) 



