A plan of a course of lectures on the principles of natural philosophy / By the Rev. S. Vince.

  • Samuel Vince
Date:
1793
Catalogue details

Licence: Public Domain Mark

Credit: A plan of a course of lectures on the principles of natural philosophy / By the Rev. S. Vince. Source: Wellcome Collection.

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    verfe ratio of the perpendiculars from the fulcrum upon the lines of di- rection, and of the length of the plane to the height. In everv machine, by diminifhing the power we increafe the time, and in the fame proportion, becaufe the velocity of the power : the ve- locity of the weight (the velocities being eltimated in the direftions in which they oppofe each other) :: the weight : the power. In the theory of this fcience we fuppofe all pianes and bodies perfectly fmooth, levers to have no weight, chords to be perfectly pliable, and machines to have no fri&ion. The allowances to be made for the difference be- ween theory and practice from thefe circumllances mud be determined by experiment. ON THE CENTER OF GRAVITY. Def. The center of gravity is that point in a body or fydem of bodies, by which, if it were fufpended, it would red in any podtion. 33. If a ftraight rod be balanced upon a ful- crum, and weights be hung upon each fide, there will be an equilibrium when the fams of the pro- duels of each weight multiplied into its dillance from the fulcrum on each fide are equal. This appears from obfervation the 5th. to prop. 22. 34. If any point be albumed in the rod, the dillance of the center of gravity from that point will be equal to the fum of the products of each body multiplied into its dillance from that point, (thofe produels being reckoned negative when the bodies lie on the contrary fide of that point to the center of gravity,) divided by the firm of the bodies. 35. The effect of any number of weights ap- plied to a lever to turn it about any point, is juft the fame as if all the weights were collected into their common center of gravity. For by the lad obfervation it appears, that the fum of the products of each body multiplied into its dillance from any point, is equal to the fum of all the bodies multiplied into the didance of their center of gravity from that point, and the effedl to turn a lever about any point js meaiured by.the body into its didance from that point; therefore con- B 2 fidering
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