IN NATURAL PHILOSOPHY. 17 



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14. Could a party play ball on the deck of the Great Eastern 

 when steaming along at the rate of 20 miles per hour, without 

 making allowance for the motion of the ship? 



They could. The ball would have the motion of the ship, 

 and would move with it in whatever direction they might 

 throw it. 



15. Since "action is equal to reaction," why is it not as dan- 

 gerous to receive the " kick" of a gun as the force of the bullet? 



The striking force is as the square of the velocity; and the 

 velocity with which the gun moves backward is as much less 

 than that with which the bullet moves forward, as the gun is 

 heavier than the bullet. For this reason a heavy gun will 

 kick much less than a light one. 



1 6. If you were to jump from a carriage in rapid motion, 

 would you leap directly toward the spot on which you wished 

 to alight? 



No ; because as one jumps from the wagon he has its for- 

 ward motion, and will go just as far ahead, while leaping, as 

 he would if he had remained in the carriage. He should, 

 therefore, aim a little back of the desired alighting-place. 



1.7. If you wished to shoot a bird in swift flight, would you 

 aim directly at it ? 



No. The bird will fly forward while the bullet is going to 

 it. One should, therefore, aim a little in advance. 



1 8. At what parts of the earth is the centrifugal force the 

 least? 



The poles. They simply turn around in 24 hours. 



19. What causes the mud to fly from the wheels of a carriage 

 in rapid motion ? 



The centrifugal force. 



20. What proof have we that the earth was once a soft mass ? 

 It is flattened at the poles. This effect is produced upon a 



ball of soft clay by simply revolving it on a wire axis. 



21. On a curve in a railroad, why is one track always 

 higher than the other? 



