. Laboratory exercises in elementary physics. II. De-termine the number of vibrations in 1, 2, and 3 minutes asbefore. Record as in Part II. Compare the average num-ber of vibrations per minute with that of similar length inPart II. Calculation.—Divide the smaller length in Part II bythe larger. Divide the smaller number of vibrations by thelarger. Compare the ratios so obtained. If they do notagree, try squaring or cubing one of the ratios, and find thevalues approximating most closely. Infer the law, and ex-press it as a formula. * Or use the method given in notes on Mensuration. ACTION AND
. Laboratory exercises in elementary physics. II. De-termine the number of vibrations in 1, 2, and 3 minutes asbefore. Record as in Part II. Compare the average num-ber of vibrations per minute with that of similar length inPart II. Calculation.—Divide the smaller length in Part II bythe larger. Divide the smaller number of vibrations by thelarger. Compare the ratios so obtained. If they do notagree, try squaring or cubing one of the ratios, and find thevalues approximating most closely. Infer the law, and ex-press it as a formula. * Or use the method given in notes on Mensuration. ACTION AND REACTION. 177 EXERCISE 8. ACTION AND EEACTION. Preliminary.—In this exercise we experiment with twobodies by giving them various amounts of energy andallowing them to collide. The special point of the experi-ment is to compare (1) the energy possessed by each bodybefore and after the collision, (2) the energy lost by onewith that gained by the other, and (3) the results of tryingelastic and non-elastic bodies. The apparatus used is shown. in Fig. 92. Two ivory balls, A and B, are so suspendedthat they can swing in one plane only, and will collide atthe lowest point of their arc. They may be drawn asideany desired distance and held there by the electro-magnetsCO, and released by breaking the circuit. The distances 178 DYNAMICS. they are drawn aside may be read on the scale by aid of thecards bb. The momentum in each case is taken as theproduct of the weight of the ball multiplied by the distanceit moved. EXPERIMENT I. Apparatus.—Two ivory balls; No. 30 wire; electro-magnets; board;two meter-sticks; electric current; circuit-breaker; tacks; made intoapparatus as shown; scales and weights (if balls are not of knownweight). Object.—To compare (1) the algebraic sums of the ener-gies possessed by two bodies before and after collision, (2)the results of trying elastic and non-elastic bodies, (3) thedirection of the action and reaction, (4) the energy lost byone with that gaine
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