1918 



Comprehensive Examination 



PHYSICS 



Monday, September 16 2-5 p.m. 



A teacher's certificate covering the laboratory instruction must be presented as a part 

 of the examination unless the laboratory notebook is to be presented at a laboratory exami- 

 nation. 



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

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



The number in parenthesis before each question indicates the number of credits 

 assigned to it. 



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

 the units used in each case. 



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



Group I 



1. A hollow box, 10X20X40 cm. on outside measurements, weighs 1,000 g. 



when empty. How many cu. cm. of stone of specific gravity 2.5 must be 

 put into the box: 



a) (4) to sink it in water ? 



b) (4) to cause it to float with -i\ of its volume above water ? 



c) (2) A vessel is moving at the rate of 8 miles per hour. A boy drops a 



ball from the mast to the deck. The ball takes 2 seconds to fall. 

 At what point will it strike the deck ? 



2. a) (3) How heavy a car can be drawn at a uniform rate along a horizontal 



track by a horse pulling parallel to the track with a force of 100 lbs. 

 if the coefficient of friction between the car and the track is 0.08? 



b) (5) If the car moves at the rate of 4 miles per hour, at what rate does the 



horse work ? 



c) (2) Why is the outer rail on a curved railway track placed higher than 



the inner rail ? 



3. A uniform horizontal bar 8 ft. long and weighing 9 lbs. is hinged at one end 



and carries a weight of 6 lbs. at the other end. The bar is supported 

 by a vertical rope attached 3 ft. from the hinge. Draw a diagram. 



a) (4) What is the tension in the rope ? 



b) (1) What is the direction of the force acting on the bar at the hinge ? 



c) (3) What is the magnitude of the force acting on the bar at the hinge ? 



d) (2) What is the mechanical advantage of the rope in raising the 6-lb. 



weight ? 



4. A 200-gram stone thrown along the surface of a horizontal sheet of ice has 



its speed reduced from 12 m. per sec. to 4 m. per sec. in 10 sec. 



a) (2) What is the acceleration (supposed to be uniform) ? 



b) (2) WTiat is the retarding force ? 



c) (4) How much kinetic energy does the stone lose in these 10 sec. ? 



d) (2) How much work is done against friction in that time ? 



(SEE NEXT PAGE) 



