High School

An organ pipe in a room at 0°C is closed on one end and open on the other. It is in tune with a violin string. If the temperature warms up to 20°C, by what fraction does the tension in the violin string need to increase or decrease to stay in tune with the organ pipe? Assume the temperature has no effect on the dimensions of the violin.

Answer :

To keep the violin string in tune with the organ pipe when the temperature increases from 0°C to 20°C, the tension in the violin string needs to increase by 0.04%.

To find the change in tension required to keep the violin string in tune with the organ pipe when the temperature increases from 0°C to 20°C, we'll use the formula relating tension, frequency, and length of the string.

Given:

- The initial temperature [tex]\( T_{\text{initial}} = 0^\circ C \)[/tex]

- The final temperature [tex]\( T_{\text{final}} = 20^\circ C \)[/tex]

- Coefficient of thermal expansion [tex](\( \alpha \))[/tex] for the violin string material

Let's proceed with the calculations:

1. Calculate the fractional change in temperature:

[tex]\[ \Delta T = T_{\text{final}} - T_{\text{initial}} = 20^\circ C - 0^\circ C = 20^\circ C \][/tex]

2. Use the coefficient of thermal expansion:

Assuming the coefficient of thermal expansion [tex](\( \alpha \))[/tex] for the violin string material is known, we can use it to find the fractional change in tension.

[tex]\[ \frac{\Delta T}{T} = \alpha \times \Delta T \][/tex]

3. Calculate the new tension:

[tex]\[ T_{\text{new}} = T_{\text{initial}} + \Delta T \][/tex]

Substitute the known values into the formulas.

Now, let's proceed with an example calculation:

Suppose the coefficient of thermal expansion [tex](\( \alpha \))[/tex] for the violin string material is [tex]\( 2 \times 10^{-5} \, \text{K}^{-1} \).[/tex]

[tex]\[ \frac{\Delta T}{T} = (2 \times 10^{-5}) \times 20 \][/tex]

[tex]\[ \frac{\Delta T}{T} = 4 \times 10^{-4} \][/tex]

[tex]\[ \frac{\Delta T}{T} = 0.0004 \][/tex]

So, the tension in the violin string needs to increase by [tex]\( 0.04\% \)[/tex] to stay in tune with the organ pipe.