File:A laboratory manual in physics, to accompany Black and Davis' "Practical physics for secondary schools," (1913) (14742102726).jpg

Identifier: laboratorymanual00blac (find matches)
Title: A laboratory manual in physics, to accompany Black and Davis' "Practical physics for secondary schools,"
Year: 1913 (1910s)
Authors: Black, Newton Henry, 1874- (from old catalog)
Subjects: Physics
Publisher: New York, The Macmillan company
Contributing Library: The Library of Congress
Digitizing Sponsor: The Library of Congress

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of the center ofgravity (<76r) of the lever, which is found by balancing thelever alone without W. What does this experiment show about where the weight of alever may be considered to act ? It will be well to arrange the results in some such way asthe following: Weight of the loaded lever g. AB AF BF BFX W FX= BFXW Wt. of Lever AX 100 g.200 g.200 g.500 g. 10.0 cm.10.0 cm.15.0 cm. Center of gravity (CG) is located cm. from A. Problem. A boy who weighs 60 lb. uses as a seesaw a15-ft. plank which weighs 70 lb. and which has its center ofgravity in the middle. If he sits 1 ft. from one end, howfar from this same end must the fulcrum be placed in orderto balance ? PARALLEL FORCES 11 EXPERIMENT 5 PARALLEL FORCES What two conditions must always exist in order to have parallelforces in equilibrium ? 4 spring balances (2000 g.).4 table clamps. Meter stick. Stout cord (fishline). Arrange the apparatus flat on the table as shown in thediagram (Fig. 6). Attach cords to the meter stick at vari-
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Fig. 6 ous points, fasten the spring balances to these cords, andarrange the table clamps so that the meter stick is aboutparallel to the edge of the table and so that all forces areparallel. 12 LABORATORY MANUAL Tighten the cords attached to F2 and Fs until the balancesindicate 1000 g. and 1500 g. respectively, and adjust F1 andF± until the whole is in equilibrium. Then read and recordthe readings of Fv Fv _F3, and F± and the distances AB, AC,AD, and AF. Repeat, using different values for Fs and JF4, and finally re-peat with different positions for C and D. Compute in each case the sum of _F2 and Fs, and the sumof F1 and Fr Compute the moment of each force about A and find ineach case the sum of the moments tending to produce clock-wise rotation and the sum of the moments tending to producecounterclockwise rotation. Compute the moments in one case about F as a turningpoint. Compare the sum tending to produce clockwise rota-tion with the sum tending to produce counterclockwiserotatilaboratorymanual00blac

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