SOME EFFECTS OF NEWTON'S LAWS 59 



another 16 inches long and compare their rates of vibration. 

 How much longer is the second than the first ? Which vibrates 

 the faster ? How much faster ? 



What one thing do you find to make a marked difference in 

 the vibration rate of a pendulum ? Try to make a statement of 

 the effect of length upon the rate of vibration. 



QUESTIONS 



1. What is inertia? State examples. Why can you not start 

 a bicycle at once at your greatest speed ? 



2. What is momentum? Upon what two factors does the 

 momentum of a body depend? How is it generally measured? 



3. A rifle ball weighing half an ounce moves at the rate of one 

 thousand feet a second, while a forty-pound cannon ball moves at 

 the rate of one foot per second. Which has the greater momen- 

 tum ? By which would you rather be struck ? Why ? 



4. Why does a woodcutter sometimes fasten his ax in a stick 

 and then invert it, striking the block with the stick uppermost ? 



5. Why can you not stand an egg on its end? If there were 

 a hole straight through the earth's center from surface to surface, 

 how far into it would a falling body go ? 



6. Under what conditions will a body be supported from 

 falling? 



7. Upon what does the stability of a body depend, and how ? 

 Why is it hard to walk upon stilts ? Why spread your feet apart 

 to receive a blow in boxing ? 



8. Explain the cause of centrifugal force. State examples of it. 

 Why do you lean in turning a corner ? Why is the inside rail of 

 a track placed lower ? What conditions increase centrifugal force ? 



9. How far will a body fall in one second? in two seconds? 

 Why does a body constantly increase in its speed as it falls? 

 Why is more damage done by a longer fall, as a rule? 



10. Describe a pendulum. What force causes it to swing down- 

 ward ? Why does it then swing upward ? If no force but gravity 

 opposed its upward swing, how far would it go as compared with 

 its downward swing ? 



