C. Summary In this experiment the velocity of sound of air in rod in two ways. The students used the Kundt’s Tube Apparatus with a meter stick, a piece of cloth, a thermometer, some rosin and Lycopodium powder. The lycopodium was evenly distributed throughout the tube which was shaken so that the powder can move and won’t have lumps. The rod in the Kundt’s Tube Apparatus is made up of brass and its length was measured. The temperature of the room was also recorded. The rosin power in the cloth was used to produce friction with the tube when the rod is stroked or rubbed horizontally producing a high pitched tone. It was done continuously until the power forms waves which are measurable and looks somewhat the same from one another. The distances of each wave was measured and the average of the half wavelengths of the sound in air column, La, was determined by dividing it to the total number of loops or segments measured. We calculate for the velocity of sound in air using recorded temperature. The value of Vr was solved. Using the Young’s Modulus and the density of the brass rod, the Vr can also be determined. The velocity of the sound in air from the textbook was compared to the obtained experimental value and theoretical value. The main objective of the experiment is to determine the velocity of sound in the rod (Vr). By performing the experiment, there are values obtained which are: the length of the rod (Lr), the average length of the half wavelength (L a), and the velocity of sound in air (Va), which is obtained from the equation
V a=
332 m +0.6(t) , where t is the room s
temperature. The velocity of sound produce in the rod can be computed using equation
the equation:
V r =V a
Lr La
since the frequency of the sound in the air is the same as
that in the metal rod. Another way to determine the velocity of sound is by using the
√
Y equation: V r = ρ
, using Young's Modulus and density of the rod.
The performed experiment tells us if we know the speed of sound in air, the speed of sound in a solid rod can be calculated based on the measurement of sound wavelength, (λ). If the frequency of the sound wave, (f) is known, we can calculate the speed of sound as: v = f λ. D. Conclusion The objectives are to determine the velocity of sound in a metal rod and to determine the speed of sound in tube applying the principles of resonance. The first objective was fulfilled since we have acquired the needed data to compute for the velocity of sound in metal rod which for example is the Young’s Modulus and density of the rod which is brass. The second objective was also achieved since the movement or the disturbance of the powder in the tube which was caused by the sound when the rod was stroke made it possible to gather data about the length of the heaps and the velocity of sound in rod can be computed. The speed of sound depends on the medium through which the waves are passing. The sound is proportional to the square root of the ratio of the stiffness of the medium and its density. The distance between two consecutive nodes or antinodes in a standing wave is half of its wavelength and the wavelength of the tone is in the rod is twice the length of the rod. Among three mediums, solid, liquid and gas, soundwaves will travel fastest in solid because the denser the medium, the faster the sound that will propagate. Solids have the strongest interactions between particles and thus the longitudinal waves travel faster than solids. Velocity is directly proportional to the Young’s Modulus and inversely proportional to the density of the rod. An application of the topic about longitudinal waves is the sound of the train whistle. The train whistles as it leaves the station and the people nearby will notice nothing unusual only the degree of intensity of someone in the platform from someone inside the carriage. As the train moves forward the intensity of the sound from someone inside will be different from someone on the platform. However if somebody is standing further ahead along the track, that individual hears the compacted sound waves. The
individual that was left from the station hears the sound waves that radiate from behind the train. It is the same train making the same sound, but since the train has compacted the sound waves before it, the waves behind it are spread out, delivering a sound of much lower frequency. Sound then varies from point of reference.
