340 



OUR PHYSICAL WORLD 



the length of board from the heavier child to the fulcrum is 

 shorter than that on which the lighter child sits. This same 

 type of lever is seen in the scales or balances which the storekeeper 

 uses to weigh his wares (Fig. 176). If you put a weight of exactly 



FIG. 176. A pair of scales 



one pound in one scalepan on the end of one arm of this lever, 

 you know you have a pound of candy on the other scalepan 

 at the end of the other equal arm when the two just balance. 



FIG. 177. The crowbar in use 



If one wants to use such a lever to raise a heavy weight, say 

 a crowbar (Fig. 177), he places the fulcrum so that the arm of 

 the lever that is under the weight is short and the arm on the 

 end of which he is pressing is long. 



