214 ANSWERS TO PRACTICAL QUESTIONS 



PNEUMATICS. 

 116. 1-18. (See Key, pp. 30-32.) 



19. Explain the theory of " sucking cider" through a 

 straw. 



The air in the straw being exhausted, the pressure of 

 the air on the cider in the vessel forces the liquid through 

 the straw. 



20. Would it make any difference in the action of the 

 siphon if the arms were of unequal diameter ? 



It would change the relative weight of the columns of 

 liquid in the two arms, and so increase or diminish the 

 difference of pressure which forces the liquid through 

 the long arm. Now, the heavier cd and the lighter ab^ in 

 Fig. 105, the faster the flow. 



21. If the receiver of an air-pump is 5 times as large as 

 the barrel, how many strokes of the piston will be needed to 

 diminish the air nearly one-half! 



One-fifth of the air in the receiver is removed at each 

 stroke. After the third stroke there would remain in the 

 receiver -ff^ of the original atmosphere. 



22. What would be the effect of making a small hole in 

 the top of a diving-bell while in use ? 



The air would escape at the top, and the water would 

 ascend and fill the bell. 



ACOUSTICS. 

 144. 1-16. (See Key, pp. 32-34.) 



