File:A laboratory manual in physics, to accompany Black and Davis' "Practical physics for secondary schools," (1913) (14764785362).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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Specific gravity of blue vitriol * Note. Subtract from the height of each column, as measured, the heightto which it was raised by capillary action at the beginning. Problem. How high would a glycerine barometer (suchas is in the South Kensington Museum, London) stand,when the mercury barometer reads 30 inches ? Sp. gr. ofglycerine = 1.26. Sp. gr. of mercury = 13.6. PABALLELOGBAM OF FOBCES 31 EXPERIMENT 16 PARALLELOGRAM OF FORCES When three non-parallel forces are acting on a body, what mustbe their relative directions and magnitudes in order to pro-duce equilibrium ? Three spring balances.Three clamps.30 cm. ruler. Fishline.Block of wood. To the middle of a piece of fishline about 40 cm. long tiea second piece about half as long. At each of the free endsmake a loop and attach the hook of a spring balance. Tothe ring of each balance attach a strong string, and thenarrange the clamps, balances, and strings as shown in Fig. 17. Pull each balance until its index is about in the middle of
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Fig. 17 32 LABORATORY MANUAL the scale where it is most reliable, and then slip a page of thenotebook under the cord connecting the balances, so thatthe knot conies about in the middle of the page. In order to show the direction of each cord on the paper,place a rectangular block alongside and draw a line directlyunder each cord. Record on each line the pull indicated bythe balance, and then relieve the tension on the spring bal-ances. Observe the zero reading of each balance and applythe proper correction to the reading just recorded. If thezero reading is less than zero, add the correction to the bal-ance reading recorded on the paper; if it is more than zero,subtract the proper amount. If the experiment has been carefully done, the three linesrepresenting the three forces will, when prolonged, intersectat a common point. Measure off on each line a distancecorresponding to the force, according to any convenient scale,such as 200 g. to 1 cm. Make an arrowhead at the endof each measur

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