# Homework Help: Beat Frequency Problem

1. Mar 23, 2010

### nietzsche

1. The problem statement, all variables and given/known data

Two strings with otherwise identical properties differ in tension by 0.25 N. If both strings are struck at the same time, what is the resulting beat frequency?

2. Relevant equations

frequency is proportional to the root of tension?

3. The attempt at a solution

I tried setting T2 = T1 - 0.25 N and substituting this into an equation with f1/f2 proportional to sqrt{T1/T2}.

But I can't seem to figure anything out from this.

2. Mar 24, 2010

### willem2

I can't make anything of it either.

If I put $f_1 = k \sqrt {T}$ and

$$f_2 = k \sqrt {T + 0.25}$$

I get

$$f_2 - f_1 = k \sqrt {T+0.25} - k \sqrt {T}$$

wich I can't simplify further.

0.25 N is probably quite small compared to the tension in the string, so we can apply

$$\sqrt {T+0.25} \approx \sqrt {T} + 0.25 \frac {1} {2 \sqrt {T}}$$

this results in

$$f_2 - f_1 \approx \frac {0.125 k} {\sqrt{T}}$$

so the answer does depend on the tension, and the other properties of the string as well.

3. Mar 24, 2010

### nietzsche

thank you so much willem. i don't think my prof worded the question properly, so i'm going to ask him tomorrow. thanks again!