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Procedure for performing real lab:
- Take the glass tube and put some powdered cork dust in it.
- By fast rotatory movement, distribute the powder uniformly inside the tube.
- Fix the tube tightly with the holder.
- Tightly clamp the metal rod at the centre.
- The piston is introduced to the other end of the glass tube.
- The rod is rubbed at B, lengthwise with a piece of rosined leather and set into longitudinal vibrations at its fundamental frequency.
- Move the piston in and out of the tube till the resonance is obtained.
- Now the cork dust inside the tube becomes deposited as heaps.
- Select the position of the extreme nodes very carefully and measure the distance between them. Find the number of heaps and calculate the average distance between two consecutive peaks.
- Note the length of the rod and repeat the experiment.
- We have the velocity of sound through air equals, 343m/s.
- Using equation (3), the velocity of sound through the rod can be calculated.
- The Youngs modulus of the rod can be calculated from equation (5).
- The glass tube must be perfectly dry as moisture afects sound velocity.
- The metallic rod should be clamped exactly at the middle.
- The powder must be evenly spread.
- The disc should not touch the glass tube, since it causes the tube to break.
Procedure for simulator:
- From the combo box Select Material select the material of the rod.
- By clicking the button Start Rubbing set longitudinal vibrations in the rod.
- Using the slider Rod length, select desired length of the experimental rod.
- The slider Piston Position helps the user to move the piston in and out of the glass tube to obtain the resonance condition. At resonance, the dust will appear as heaps.
- Using this slider Scale Position, move the ruler and measure the length between the desired number of heaps. From that, one can calculate the length of one heap.
- The option Show Result displays the velocity of the sound waves and the Young's modulus of the material of the rod.
- The Reset button resets the conditions.
- The experiment can be repeated for different materials of rod and different rod lengths.
Length of the rod, lr= …………… m.
Frequency of sound used, f = ………. Hz.
Velocity of sound in air, Va = 343 m s-1.
Mean la = ……………. m.
The velocity of sound wave through the rod = ………………… m s-1.
Young’s modulus of the material of the rod = ………………. N m-2.