# Effect Of Tension On Resonance And Amplitude

Effect Of Tension On Resonance And Amplitude planning Aim The aim of the experiment is to investigate the effect of tension on resonance and amplitude of a string. Basis Personal Knowledge This experiment is based on the resonance, frequency and amplitude. From what I have learnt in class and everyday life, I know that when a string of any kind is plucked, it moves to and fro. The movement causes the air molecules around it to vibrate. When it moves fast enough, the vibrations cause a sound to be heard. Research Some research was carried out into the principles on which the experiment is based. The frequency of an oscillation is defined as the number of cycles executed per unit time (Salters Horners Advanced Physics) That is for a spring the time taken for it to move to and fro once is its frequency. Frequency is measured in Hertz (Hz). Each object has its own natural frequency. (Physics For You by Keith Johnson). Resonance occurs when the applied frequency equals the natural frequency of the object. Therefore when the string to be used in the experiment is plucked and the applied frequency equals its natural frequency then resonance occurs. The resonant frequency of a string can be increased by:
Shortening the length
Increasing the tension
Using a lighter stringVariables and Constants The experiment is basically concerned with the effect that the tension will have on the frequency and amplitude. Therefore, the basic variable will be the tension of the string. The constant in this case would be the thickness of the string, as it will not be changed. This should ensure that the experiment is fairly accurate as its thickness can affect the resonance. Application of Principles The principles of frequency, resonance and amplitude are largely applied in many engineering projects. The understanding of the above principle is vital to ensure that bridges are safe to travel on. They are applied in musical instruments to make sounds of varying frequencies, loudness and pitch. Eco-sounding, which uses the understating of frequency, is used to locate shoals of fish. Dolphins and bats use it to find their way and the latter uses it to hunt for prey. Apparatus The following are the apparatus need to carry out the experiment:
Sound box
String
100g masses
Diagram of apparatus [image] Prediction From personal knowledge and research, it can be predicted that increasing the tension will increase the amplitude as the resonant frequency increases. implementing Safety Safety is always a priority when carrying out an experiment of any kind. It was necessary to ensure that the workspace was free of obstacles. Care was taken not to drop the masses in order to prevent injury. Procedure The following are the steps that were used to carry out the experiment: 1. Care was taken to ensure that the workspace was free of obstacles. 2. One end of a string was fastened to one end of the sound box. 3. The other end was dropped to the pulley end of the sound box and fastened to a 200g mass. 4. It was made certain that the knots were tight and then the string was plucked. Observations were made to ensure that the string was secure enough. 5. When it was certain that the string was secure enough, it was plucked and observed. Emphasis was placed on the frequency and the amplitude. The observations were recorded. 6. Another 200g mass was added to make 400g and steps 4 and 5 were repeated. 7. Steps 4 and 5 were repeated by adding 200g mass to the previous mass until the mass was 1200g. The above procedures were repeated. When the experiment was completed, the workspace was tidied up, taking care not to drop the mass or the string to prevent injury. observing and recording Observations Each time the mass on attached to the string was increased it became tighter. This resulted in an increase in its tension. Results When the string was plucked with a 200g mass attached, a soft sound was heard. When the mass was increased to 400g, the sound became harder and louder. The string also vibrated longer than at 200g. Also the frequency at which the string vibrated was higher at 400g than at 200g. Since it vibrated faster at 400g than at 200g, resonance occurred faster at 400g than at 200g. This result was found to be consistent with subsequent readings, in that whenever the mass on the string was increased, the frequency of the waves produced was larger than the previous mass. interpretation and evaluation Interpretation From knowledge and research, it is known that an increase in the tension of a string will increase its resonant frequency. This was the case when the mass on the string was increased from 200g o 400g and therefore increasing its tension. It was also found that the amplitude of the waves produced with a bigger mass on the string, was bigger than those produced with smaller masses. Increasing the mass on the string and thereby increasing its tension caused a louder sound to be heard because there was an increase in the amplitude. Since the loudness of a sound wave depends on the amplitude, a higher frequency produced larger amplitude, which produced a louder sound. Improvements This was a basic experiment and was not very accurate since no accurate measuring instruments. As a result the accuracy of the results obtained cannot be guaranteed although a general measure of accuracy can be assured. The experiment can be improved by connect a microphone to a cathode ray oscilloscope, which would give an accurate waveform which can then be studied. Conclusion Although this was not a very accurate experiment, the general results seemed to agree with the prediction made in the planning. An increase in a string?s tension will cause an increase in its resonant frequency, thereby increasing its amplitude and the loudness of the sound produced when plucked.

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