PENDULUMS. 



The vibrations of pendulums are as the square roots of 

 their lengths. The length of one that will vibrate seconds 

 in New York, at the level of the sea, is 39.1013 inches. 



To Jmd the length of a pendulum for any given number 

 of vibrations per minute. 



RULE. As the number of vibrations given is to the 

 square root of 39.1013 inches, so is 60 to the square root 

 of the length of the pendulum required. 



EXAMPLE. What is the length of a pendulum that will 

 make 50 vibrations per minute ? 



