A) 186 Hz
B) 220 Hz
C) 276 Hz
D) 312 Hz
Correct Answer: C
Solution :
Let the frequency of the fork be n. In the first case, the length of the wire is 70cm. Therefore, \[n=\frac{1}{2\times 70}\sqrt{\frac{T}{m}}\] ?. (i) On decreasing the length of the wire, its frequency will increase. Hence, in the second case when the length is 69cm, then \[n+4=\frac{1}{2\times 69}\sqrt{\frac{T}{m}}\] .... (ii) Dividing Eqs. (i) by (ii), we get \[\frac{n}{n+4}=\frac{1/70}{1/69}\] \[\Rightarrow \] \[\frac{n}{n+4}=\frac{69}{70}\] \[70n-69\,n=69\times 4\] \[n=276\,Hz\]You need to login to perform this action.
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