MECHANICS.

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Chap. l.J

Th is scale shows at one view, all the laws observed byfalling bodies. The body O would fall from O to 1, equalto 16,2 feet, in the first second, and acquire a velocitythat would carry it 32,4 feet from I to a, horizontally,in the next second, by laws 5 and 6; this velocity wouldalso carry it down to three in the same time; but its gra-vity, producing equal effects, in equal times, will acce-lerate it so much as to take it to 4 in the same time, bylaw 1. It will now have a velocity of 64,8 feet per se-cond, that will take it to b horizontally, or down to 8,but gravity will help it on to 9 in the same time. Itsvelocity will now be 97,2 feet; which will take it hori-zontally to c, or down to 15, but gravity will help it onto 16; and its last acquired velocity will be 129,6 feet,per second, which would carry it to d horizontally.

If either of these horizontal velocities be continued,the body will pass over double the distance it fell, in thesame time, by law 6.

Again, if 0 be perfectly elastic, and falling, strikes aperfectly elastic plane, either at 1,3, 5, or 7, the effec-tive force of its stroke will cause it to rise again to O inthe same space of time it took to fall.

This shows, that in every equal part of distance, itreceived an equally effective impulse from gravity, andthat the total sum of the effective impulse is as the dis-tance fallen directly—and the effective force of thestroke will be as the squares of the velocities, by laws 7and 8.

article 11.

OF BODIES DESCENDING INCLINED PLANES AND CURVEDSURFACES.

Bodies descending inclined planes and curved sur-faces, are subject to the following laws:—

1. They are equably accelerated, because their mo-tion is the effect of gravity.

2. The force of gravity propelling the body A, fig. 5,to descend an inclined plane A D. is to the absolute gra-

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