As 8 : 2 :: 120 : 30 lb. Ans.
Example 2.—A beam, 20 feet in length, and supported at both ends, bears a weight of 2 tons at the distance of eight feet from one end; required the weight on each support?
40 cwt. × 8 feet 20 feet = 16 cwt. on the support that is furthest from the weight; and 40 × 12 20 feet = 24 cwt. on the support nearest to the weight.
Case 3.—When the weight to be raised is at one end of the lever, the fulcrum at the other, and the power is applied between them.
Rule.—As the distance between the power, and the fulcrum, is to the length of the lever, so is the weight, to the power.
Example.—The length of the lever being 8 feet, and the weight at its extremity 60 lb., required the power to be applied 6 feet from the fulcrum to raise it?
As 6 : 8 :: 60 : 80 lb. Ans.
Velocity is gained at the expense of power by the lever, and wheel, and axle.
Note 1.—When two men are carrying a load on a pole between them, the strongest man should have the weight placed nearer to him than the other man.
Note 2.—To carry guns, &c.—If the burden can be carried by four men; after having made it fast to the middle of a large lever, fix the extremities of this lever on two shorter levers, and place a man at each of the points, C, D, E, F. Vide plate, Mechanics, [Fig. 1.] In [Fig. 2], the weight is equally divided between eight men, and in [Fig. 3], between sixteen men.