. Laboratory exercises in elementary physics. he force is over-come directly ? For example, if a weight is lifted directly10 ft., or lifted the same distance by a machine, is thework done in the former case any more than that done inthe latter ? To answer this question, we may raise a knownweight a known vertical distance by means of a machine,—say an inclined plane,—and compare the work done in thiscase with that done in lifting the body vertically the samedistance. For this purpose the apparatus illustrated inFig. 89 may be used. The board B forms the inclinedplane, and may be set at any ang
. Laboratory exercises in elementary physics. he force is over-come directly ? For example, if a weight is lifted directly10 ft., or lifted the same distance by a machine, is thework done in the former case any more than that done inthe latter ? To answer this question, we may raise a knownweight a known vertical distance by means of a machine,—say an inclined plane,—and compare the work done in thiscase with that done in lifting the body vertically the samedistance. For this purpose the apparatus illustrated inFig. 89 may be used. The board B forms the inclinedplane, and may be set at any angle by adjusting the rod Rof the support S. The weight to be raised is the loadedcarriage C, and the force required to pull it up the planemay be obtained from the reading of the balance B. Wecan get the work done in raising the body vertically bymultiplying the total weight of the body by the distance it 170 DYNAMICS. is raised (say ab in the figure), and the work done in rais-ing it by the plane by multiplying the force required to pull. Fig. 89. the body up the plane by the distance that it must travelon the plane, cb in the figure, to reach the required height. EXPERIMENT. Apparatus.—Board of Exercise 2; support; weighted carriage;24-lb. balance; cross-stick and cord; meter-stick; T-square orplumb-line. Object.—1. To study the laws of the inclined plane. see if a machine, taking the inclined plane as an exam-ple, saves work. Manipulation.—Get the weight of the carriage andload together.* In case no suitable scales can be had, theweight may be found with sufficient accuracy by means ofthe spring-balance. Adjust the support so that the boardB is inclined at an angle of about 30 degrees. Hook thebalance into the loop at the end of the cord connected withthe carriage. Let one student hold the balance firmly inboth hands, and draw the carriage up the plane at a uni-form rate of speed. The back of one hand should rest onthe board upon which it slides, and his entire
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