MOMENTUM. EXAMPLES. 



15 



An Eastern traveler once succeeded in saving his life by 

 a ready knowledge of this principle. He was closely pur- 

 sued by a tiger, and when near a precipice, watching his 

 opi^ortunity, he threw his coat and 

 hat on a bush, and jumped one 

 side, when the animal, leaping swift- 

 ly on the concealed bush, was car- 

 ried by momentum over the prec- 

 ipice. 



As a large or heavy body pos- 

 sesses greater momentum than a 

 small or light one, so any body 

 moving with great speed possesses 

 more than one moving slowly ; for 

 instance, the momentum of a rifle 

 ball is so great as to carry it through 

 a thick plank, while, if thrown slow- 

 ly, it would scarcely indent it. 



This property of bodies is applied 

 with great advantage to many 

 practical purposes. The momentum 

 of the hammer drives the nail into 

 the wood; for the mere pressure 

 of its weight would not do it, if it 

 were a hundred times as heavy. 

 AYedges are driven by employing 

 the same kind of j^ower. 



On a larger scale, the pile-engine 

 operates in a similar manner. The 

 ram or weight, h (fig. 4), is slowly 

 lifted by means of a pulley and 

 wheel-work, Avorked by the handles or cranks, h h^ until 

 the arms of the tongs which hold the ram are compressed 

 in the cheeks, i ?, when it suddenly falls with prodigious 

 force on the pile or post to be driven. In this way long 

 posts of great size are forced into the mud of swamps and 



clk=^ 



Pile Engine. 



