1918 

 Comprehensive Examination 



PHYSICS 



Friday, June 21 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 ntmibered questions, distributed as follows: three from Group I, two from 

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



The niunber in parenthesis before each question indicates the nimiber 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 wooden cube 5 cm. on an edge weighs 100 g. 



a) (3) What is the density of the cube ? 



b) (3) What force would be required to hold the cube submerged in a liquid 



having a density of 1 .5 g. per cu. cm. ? 



c) (4) How much of its volume would protrude above the surface if the 



cube were floated in a liquid having a density of 1 .2 g. per cu. cm. ? 



2. a) (3) Define work; mechanical advantage of a machine; efl&ciency of a 



machine. 

 b) (7) Two men raise a weight by means of a jackscrew. They push with a 

 force of 100 lbs. each, at opposite ends of a bar 5 ft. long that passes 

 through a hole at the top of the screw. If the pitch of the screw is 

 I inch and the efi&ciency of the machine is 30 per cent, how great is 

 the weight ? 



3. An engine operates a pump which raises water to a height of 50 ft. at the rate 



of 1,000 gal. per min. (One gallon of water weighs 8.4 lbs.) 



a) (3) How much work is done upon the water per second ? 



b) (7) If the efficiency of the pump is 90 per cent, how many horse-poM^er 



is the engine developing ? 



4. A constant force acting on a mass of 40 grams for 5 seconds changes its 



velocity from 60 cm. per second to 100 cm. per second. What is: 



a) (2) the acceleration ? 



b) (2) the magnitude of the force? 



c) (2) the total distance covered in the five seconds ? 



d) (2) the final momentum ? 



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



(SEE NEXT PAGE) 



I2S . 



