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Show THE MECHANICS OF THE WHEELBARROW Longer Handlea Increase the Lovcrase and' LlRhtun the Load By C. J. t.ynde, Mocdonald College. The principle of tho wheelbnrrow Is tho sarao as that of the crowbar. For ..example, If n rann la standing still and Is smply lifting a weight on a wheelbarrow, wheel-barrow, then the axlo of tho wheel Is tho turning point or fulcrum. If tho distance from the axle to th0 hands Is C feot and, from tho axlo to a lino drawn vertically downwards from tho j center of tho weight Is 2 feot, then tho levorago Is G to 2 or 2 to 1, and 100 pounds of forco exerted upwards by the hands will lift 250 pounds of weight on the barrow. If tho load Is piled up over tho wheel so that a line drawn vertically downwards from the center passes ono foot from tho axle, then the levorago 1b 5 to 1, and 100 pounds of force will 'lift GOO pounds of weight on the barrow. This explains why tho Bmall boy, and tho big boy, too, nlways loads thia way. in these calculations tro havo left out of account tho forco necessary to lift tho handles when tho barrow Is empty; from 10 to 1G, pounds is necos-Fnry necos-Fnry for this In tho ordinary barrow. If the wheelbarrow Is moved along the liS If tho handles were mado 6 feet long the leverage would be C to' 2 or 3 to 1. Tho hands would lift 1-3 of 100 pounds, 33 1-3 or 1C 2-3 pounds each. Long handles then arc an advantage, as far as tho lifting forco Is concornod. They have still nnother advantage. With tho short handles, the slant from the hands to tho axles Is sharp. Th'e force used In moving tho barrow is exerted along this slant and about ono-fdurth of It Is wasted In shoving about tho wheel Into tho ground. The other three-fourths Is what moves the barrow ahead. With tho long handlos tho slant is less sharp; thorcforo more of tho moving force Is used to movo tho barrow and less Is wasted In shoving, shov-ing, tho wheel deeper Into the ground. Long handles thon are an advantage, ns to lifting forco and also as to moving mov-ing forco. In using a pitchfork ono hand works twice ns hard as tho other. To provo this, consider that ono is using a fork loft-handed. Tho left hand grasps tho center of tho handle and tho right tho end.. In carrying Advantage of Long Handles Illustrated road, still more forco will be necos-sury, necos-sury, and the amount will depend on the load and Its position with respect to tho wheel and on the nature of the road. The barrow belongs to lovers of tho second class and this class of lever Is Identified by tho fact that tho weight always comes between tho forco and the fulcrum. Other examples of this class of levers 'are tho gate, the door, and nut-crackers. S 1 Long handles on a wheelbarrow aro ii decided advantage. In tho ordinary garden wheelbarrow tho handles nrc about four feot long. This Is the dlstanco from tho axle to the center of the hand grip. If a weight of 100 pounds Is placed on tho barrow In, such a position that tho confer con-fer of It Is 2 feet from tho axlo tho loverage Is 1 to 2, or 2 to 1. The liands lift one-half of 100 pounds, or 50 pounds, tliat is, 25 pounds each. If tho handlos were mado 5 feet long with the weight In tho same position, po-sition, tho leverage would bo G to 2. Tho hands would lift 2-5 of ;00 pounds, 40 pounds, or 20 pounds each. hay with tho fork In n horizontal position po-sition tho left hand lifts up and the right hand shoves down. How touch forco does each hand ex-ort? ex-ort? A forkful of hay weighs about 15 pounds. Tho left hand being In the middle, the right hand must push down with a forco of 15 pounds to balance bal-ance the weight of tho hay. The left hand lifts against the weight of tho hay 1G pounds, and against the downward down-ward push of tho right hand 1G pounds more, or 30 pounds altogether. Tho' right hand shoves downward 15 pounds and tho left hand lifts 30 pounds, and therefore thq left hand exerts ex-erts twice tho force that the right hand does. As a matter of fact tho left hand does a llttlo more than this, becauso It lifts the weight of the fork, which amounts to about three pounds more. When tho hay Is lifted up and carried car-ried with the fork in a vertical position posi-tion each hand will carry half tho weight, or the left hand will bo used Just to steady tho fork and tho right hand to enrry It all, 15 pounds of hay and thrco pounds of fork. |