64 APPLIED SCIENCE 



or F 2 



20 



Impulse equals force times time. Impulse may be defined 

 as the force multiplied by the length of time it acts. 



Weight X Velocity 

 Momentum = 



32 



The energy stored in a revolving fly-wheel is kinetic, and 

 is, therefore, represented by the formula 



WV 2 



K = 



20 



W stands for, or is equal to, the weight of the wheel in pounds, 

 g for 32, attraction force of gravity, V for velocity of a de- 

 finite point in the iron in feet per second. At this 

 definite point the whole weight is assumed to be 

 collected. 



64. Springs as a Source of Energy. Springs are 

 useful as machine parts, because of their capacity 

 for yielding to force without permanently losing their 

 shape technically called their "permanent set." 

 Wound springs possess potential energy, because at 

 some previous time work has been performed upon 



FIG 40 them in the winding. Coiled springs in watches and 



Coiled clocks which set the mechanism in motion, are an 

 illustration. Steel is superior to all other materials 



for the manufacture of springs, but must be protected when 



exposed to dampness; otherwise it will rust. 



