Page 258 - Third Book of Reading Lessons

READING LESSONS.
bring it to the ground; and the ball goes to a rther or less distance in proportion to the quantity of pow­ der used.
Tbe third law of motion is,-" that to every ac­ tion one body upon another, t ere is an equal and contrary re-cwtion." If I strike this table, I com­ municate to it (which you perceive by the shaking of the china-ware) the motion of my hand; and the
• table re-acts against my hand just as much as my hand acts against the table. In all cases the quan­ tity of motion gained by one body is always equal to that lost by the other in the same direction. Thus, if a ball in motion strike another at rest, the motion communicated to the latter vill be taken om the rmer, and the velocity of the rmer will be pro­ portionally diminished. A horse drawing a heavy load is as m_uch drawn back by the load as he draws it rward.
EMMA.-I do not comprehend how the cart draws the horse.
F THER.-But the progress of the horse is im­ peded by the load, which is the same thing; r the rce which the horse exerts would carry him to a greater distance in the same time, were he eed from the incumbrance of the load; and there re, as much as his progress lls short of that distance, so much is he, in e ect, drawn back by the re-action of the loaded cart.
From this law of motion you may learn in what manner a bird, by the stroke of its wings, is able to support the weight of its body.
CH RLEs.-Pray explain this, papa.
FATHER.-If the rce with which it strikes the air 22*
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