Conservation of Energy 



FIG. 31. When the handle is turned the blades of the egg beater move much 

 more rapidly than the hand. Will they pinch hard enough to hurt? 



of the string. Notice that it is not harder or easier to move 

 the pail when it is near the nail than when it is near the floor. 

 When your hand moves down from the nail to the floor, how 

 far up does the pail move ? Does the pail move a greater or 

 less distance than your hand, or does it move the same 

 distance ? 



Next fasten one end of the string to the nail. Set the 

 pail on the floor. Pass the string through the handle of 

 the pail and up over the spool (Fig. 33). Pull down on the 

 loose end of the string. Is the pail easier to lift in this way 

 or in the way you first tried ? As you pull down with your 

 hand, notice whether your hand moves farther than the pail, 

 not so far as the pail, or the same distance. Is the greater 

 amount of motion in your hand or in the pail? Then where 

 would you expect the greater amount of force? 



The whole idea of the lever can be summed up like 

 this: one end of the contrivance moves more than the 

 other. But energy cannot be lost; so to make up for 



