Q8 Dr Semie, A hifilar method of measuring the rigidity of wires 



Simple interpolation, by "proportional parts," will give s with 

 an error not exceeding unity in the fifth place of decimals. Thus, if 

 tan xfs = •124, we find s = "00095, and then 



sin i/f = tan i// - 5 - •12305. 



§ 7. Practical example. The following results were obtained for 

 a pair of soft brass wires. 



The distances AO, BD were each 6^00 cm. Hence aj = ag = 3 cm. 



Mean radius of wires = r = 0^0352 cm. 



Length of each wire = I = 47^30 cm. 



Mass of suspended system, excluding the weight W (Fig. 2) = 417^6 gm. 



The small correction for the buoyancy of the damper was neglected. 



The deflexions were observed by a goniometer. The distance from the 

 centre of the pivot to the scale was 40^00 cm. The central, or zero, reading is 

 10-00 cm. The following goniometer readings were obtained for the last 17 of 

 the values of specified in § 5. 



The value of x was found by subtracting from the mean reading, as given 

 in column 4, the mean zero reading 9-985 cm. corresponding to (^ = 0. The 

 differences between the readings in columns 2 and 3 are due to hysteresis. The 

 seventh column shows that sin i3 is not proportional to <p. 



