- Home
- Standard 11
- Physics
A string under a tension of $129.6\,\, N$ produces $10\,\, beats /sec$ when it is vibrated along with a tuning fork. When the tension is the string is increased to $160\,\, N,$ it sounds in unison with same tuning fork. calculate fundamental freq. of tuning fork .... $Hz$
$100$
$50$
$150$
$200$
Solution
frequency of tuning fork $ = \frac{{\sqrt {\frac{{160}}{{\rm{m}}}} }}{{2l}}$
According to the question
$\frac{1}{{2l}}\sqrt {\frac{{160}}{{\rm{m}}}} – \frac{1}{{2l}}\sqrt {\frac{{129.6}}{{\rm{m}}}} = 10$
$\frac{1}{{2l}}\sqrt {\frac{{10}}{m}} [4 – 3.6] = 10 \Rightarrow \frac{1}{{2l}}\sqrt {\frac{{10}}{m}} = 25$
so ${{\rm{V}}_{{\rm{TF}}}} = \frac{1}{{2l}}\sqrt {\frac{{160}}{{\rm{m}}}} = 4\left[ {\frac{1}{{2l}}\sqrt {\frac{{10}}{{\rm{m}}}} } \right] = 100\,{\rm{Hz}}$