14. The effective length of the head of a hammer is 2 in. The handle is 15 in. long and the nail holds in the wood with a force of 500 lbs. Only 60 lbs. of force is available at the end of the handle. What will be the result?
15. If an effort of 50 lbs. acting on a machine moves 10 ft., how far can it lift a weight of 1000 lbs.?
16. A bar 10 ft. long is to be used as a lever. The weight is kept 2 ft. from the fulcrum. What different levers can it represent?
17. The effort arm of a lever is 6 ft., the weight arm 6 in. How long will the lever be? Give all possible answers.
18. Two boys carry a weight of 100 lbs. on a pole 5 ft. long between them. Where should the weight be placed in order that one boy may carry one and one-fourth times as much as the other?
(4) The Wheel and Axle and the Pulley
124. The Wheel and Axle.—1. One of the simple machines most commonly applied in compound machines is the wheel and axle. It consists of a wheel H mounted on a cylinder Y so fastened together that both turn on the same axis. In Fig. 90, ropes are shown attached to the circumferences of the wheel and axle. Sometimes a hand wheel is used as on the brake of a freight or street car, or simply a crank and handle is used, as in Fig. 91. The capstan is used in moving buildings. Sometimes two or three wheels and axles are geared together as on a derrick or crane as in Fig. 92.
Fig. 90.—The wheel and axle.
Fig. 91.—Windlass used in drawing water from a well.
Fig. 92.—A portable crane.
Fig. 93.—The wheel and axle considered as a lever.
