1917 



Comprehensive Examination 



PHYSICS 



Friday, June 22 2-5 p.m. 



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

 of the examination, imless the laboratory notebook is to be presented at a laboratory 

 examination. 



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. If a 10-gram body should start from rest down a frictionless plane and gain 



in six seconds a velocity of 120 cm. per second, what would be: 



a) (2) tlie total distance covered ? 



h) (2) the distance covered during the first second ? 



c) (2) the distance covered during tlie last second ? 



d) (2) the acceleration ? 



e) (2) the kinetic energy at the end of six seconds ? 



2. a) (2) Define horse-power. 



b) (6) An automobile running at the constant rate of 30 miles per hour 



exerts a force of 200 lbs. in the direction of motion. What is the 

 power supplied to the wheels of the automobile ? 



c) (2) If the efl&ciency of the transmitting mechanism is 75 per cent, what 



horse-power is the engine developing ? 



3. a) (7) A uniform plank, AB, 12 ft. long and weighing 80 lbs., is used as a 



"diving-board." End A is fastened to the floor of a float. Four 

 ft. from A the plank rests on the slightly raised edge C of the float, 

 so that 8 ft. of the plank projects over the water. A boy weighing 

 100 lbs. stands on end B and a second boy of 60 lbs. weight, 1 ft. from 

 him. Under these conditions, how strong must the fastenings be 

 at^.? 

 h) (3) What is the direction and magnitude of the force exerted at C? 

 Make a diagram. 



4. a) (7) A building is being moved on rollers on a level road by means of a 



capstan (a form of the wheel-and-axle machine). Two horses, each 

 exerting an effective pull of 125 lbs., are attached to the capstan 

 bar (wheel) at a distance of 7 ft. from the center of the drum (axle). 

 This drum, on which the ro])e attached to the house is wound, is 

 G in. in diameter. If the coefficient of friction of the building on the 

 rollers is 0.3, what is the weight of the building? Neglect other 

 friction. 

 b) (3) If the horses make 5 circuits per minute, what is the rate of working 

 of the team ? 



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