1918 

 PHYSICS 



Friday, June 21 2 p.m. Two hours 



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. 



Group I 

 {Omit one question from this group.) 



1. (a) Explain the meaning of the terms acceleration, work, power, momentum, 



moment of a force. 

 (b) A balance has unequal arms, the left-hand arm having a length 99 per 

 cent of that of the right-hand arm. A dealer has the habit of putting 

 in the left-hand pan the articles which he sells. Who gains, the dealer 

 or the customer ? Why ? 



2. The water passing through the turbine water wheels at the Niagara power 



plant has fallen 136 feet. The average horse-power of the turbines is 5,000 

 and their efficiency is 85 per cent. How many cubic feet of water does 

 each turbine discharge per minute? (One cubic foot of water weighs 

 62 . 4 pounds.) 



3. A painter's platform is 18 feet long and weighs 100 pounds. Its center of 



gravity is 8 . 5 feet from the right-hand end. The platform is hung in a 

 horizontal position by two ropes, one attached one foot from one end, the 

 other one foot from the other end. When a painter weighing 150 pounds 

 stands at a point 7 feet from the left-hand end of the platform, what 

 weight does each rope support ? 



4. An aeroplane one mile above the earth is moving horizontally with a velocity 



of 60 miles per hour. A bomb is dropped from it in an attempt to hit a 

 station. When the bomb is released, how far should the aeroplane be 

 from the point ahead in its path which is directly over the station ? 



Group II 

 (Omit one question from this group.) 



6. Describe an experiment, preferably one which you have personally performed, 

 by which the wave-length of a musical sound may be determined. 



6. A man is standing two miles in front of a cliff. A gun, located between the 

 man and the cUff , is fired. The man hears the report of the gun and, four 

 seconds later, hears the echo of the report from the cliff. Taking the 

 temperature of the air as 0° C., fmd the distance from the gun to the cliff. 



(SEE NEXT PAGE) 



