Procedure

Apparatus:

A long glass tube, piston, metal rod, powdered cork, ruler, clamps and leather piece.

Procedure for Performing Real Lab:

1. Take the glass tube and put some powdered cork dust in it.
2. By fast rotatory movement, distribute the powder uniformly inside the tube.
3. Fix the tube tightly with the holder.
4. Tightly clamp the metal rod at the centre.
5. Introduce the piston to the other end of the glass tube.
6. Rub the rod at B, lengthwise with a piece of rosined leather and set it into longitudinal vibrations at its fundamental frequency.
7. Move the piston in and out of the tube until resonance is obtained.
8. The cork dust inside the tube becomes deposited as heaps.
9. Select the position of the extreme nodes carefully and measure the distance between them. Find the number of heaps and calculate the average distance between two consecutive peaks.
10. Note the length of the rod and repeat the experiment.
11. The velocity of sound through air is taken as 343 m/s.
12. Using equation (3), calculate the velocity of sound through the rod.
13. Using equation (5), calculate the Young's modulus of the rod.

Note:

• The glass tube must be perfectly dry as moisture affects 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, as it may cause the tube to break.

Procedure for Simulator:

1. From the combo box Select Material, select the material of the rod.
2. Click the Start Rubbing button to set longitudinal vibrations in the rod.
3. Use the Rod Length slider to select the desired length of the experimental rod.
4. Use the Piston Position slider to move the piston in and out of the glass tube to obtain resonance. At resonance, the dust will appear as heaps.
5. Use the Scale Position slider to move the ruler and measure the length between the desired number of heaps. From that, calculate the length of one heap.
6. The Show Result option displays the velocity of sound waves and the Young's modulus of the rod material.
7. Click the Reset button to reset the conditions.
8. The experiment can be repeated for different materials and rod lengths.

Observations:

• Length of the rod, l_r = …………… m
• Frequency of sound used, f = ………. Hz
• Velocity of sound in air, V_a = 343 m/s

Mean l_a = ……………. m

Use equation 3 to calculate $V_r$ and equation 5 to calculate $Y$.

Result:

• The velocity of sound wave through the rod = ………………… m/s
• Young’s modulus of the material of the rod = ………………. N/m²