3.14.4 Experiment procedures
1)Determine the linear density of the string
Fix the tension(which can be obtained from the weight and the mass of the plate)and the distance between the two wedge tips A and B,and adjust an appropriate frequency so that the standing waves with multiple antinodes appear on the string.Record the distance L between the two wedges A and B when one,two,and three antinode segments are formed,respectively,then calculate λ and ρ according to Equation(3.14.4)and Equation(3.14.8).Afterwards,calculate their average value and compare with the theoretical value ρ and determine the percentage error.
2)Determine wave speed
Under constant tension T and fixed string length(0.9 m),change the frequency to realize different standing wave conditions with n=1,2,3 antinodes on the string.Record the corresponding f,n,L,and calculate the transverse wave velocity V on the string from Equation(3.14.6),and compare it with the theoretical value to find the percentage error.
3)Determine frequency(https://www.daowen.com)
With a fixed frequency(100 Hz),change the weight value and adjust the distance between two wedges A and B,so that 1,2 or 3,…standing wave antinodes appear on the string.Record the distance between A and B,and measure the frequency of string vibration according to Equation(3.14.7),and compare it with the selected frequency(100 Hz)to calculate the percentage error.
4)Tips and Attentions
(1)After changing the weight hanging on one end of the string,make sure that the weight is stable before measuring.
(2)At some frequencies(near 60 Hz),the amplitude is too large due to the resonance of the vibrating reed.At this point,the knob on the panel should be turned counterclockwise to reduce the amplitude for the experiment(it is better to avoid the resonance point for the experiment).When the vibration is not working at the resonance frequency,the amplitude knob 4 in Figure 3.14.2 can be adjusted to the maximum output.
