Supplement to the first edition of ... elements of physics, or natural philosophy / [Neil Arnott].

  • Arnott, Neil, 1788-1874
Date:
1828
Catalogue details

Licence: Public Domain Mark

Credit: Supplement to the first edition of ... elements of physics, or natural philosophy / [Neil Arnott]. Source: Wellcome Collection.

    12/38
    At page 133, before last line 136). Another case of the lever, exhibited in the adjoining diagram, serves well to explain the nature of mechanical powers in general. Suppose A to be a weight of four pounds at the end of the rod or lever A B, turning on C as its axis, or fulcrum, and having the arm C B four times as long as the arm CA.: one pound at the end e B, would balance the four pounds at the end A (the wei«'ht of the lever itself is not retrarded here), and with the slightest additional weight would preponderate. Now let us suppose the arc B h fixed to the long arm of the lever, and having four projections or shelves from it, on which balls of one pound might rest: if one of the four balls from the plane d were to roll upon the first shelf, with one grain more, it would lift A, and would itself descend to plane c, one inch below; then a second ball of one ])ound would occupy the second shelf, and would descend in the same way, and then a third, and then a fourth; and when the whole four had fallen from d to c, they Avon Id just have lifted the four pound weight, at the other end of the lever, one inch. Then, although one pound were seen here lifting four pounds, it Avould only lift it one- fourth part as far as it fell itself, and the sum of the phenomenon, Avhen ended would be, that four pounds, by falling one inch at the long end of the lever, would have lifted four pounds one inch at the short end. No mechanical power or machine generates force more than the lever in this case. At page 134, after last line {* p. 137). We must warn the reader, however, that there ai-e many important considerations connected with the ]n'at'- tical employment of forces, according to their respective nature, and that of the resistance (o be overcome, which