MCQ
The vibrations of a string of length $60\, cm$ fixed at both the ends are represented by the equation $y = 2\,\sin \,\left( {\frac{{4\pi x}}{{15}}} \right)\,\cos \,\left( {96\pi t} \right)$ where $x$ and $y$ are in $cm$. The maximum number of loops that can be formed in it is
  • A
    $6$
  • $16$
  • C
    $5$
  • D
    $15$

Answer

Correct option: B.
$16$
b
Suppose the string vibrates in $\mathrm{p}$ loops. Wavelength of the $\mathrm{p}^{\text {th }}$ mode of vibration is given by :

$\therefore \lambda_{\mathrm{p}}=\frac{2 l}{\mathrm{p}}$        ........$(i)$

Given that, $y=2 \sin \left(\frac{4 \pi x}{15}\right) \cos (96 \pi t)$

$=2\left[\sin \left(\frac{4 \pi \mathrm{x}}{15}+96 \pi \mathrm{t}\right)+\sin \left(\frac{4 \pi \mathrm{x}}{15}-96 \pi \mathrm{t}\right)\right]$

Comparing it with standard equation, we get

$\mathrm{v}=\frac{\omega}{2 \pi}=\frac{96 \pi}{2 \pi}=48 \mathrm{\,Hz}$

 and $ \quad \mathrm{K}=\frac{4 \pi}{15}=\frac{2 \pi}{\lambda_{\mathrm{p}}} \quad$ or 

$\lambda_{\mathrm{p}}=\frac{15}{2}$

from eq. $(i)$ we get,

$\frac{15}{2}=\frac{2 \times 60}{\mathrm{p}} $ or $ \mathrm{p}=16$

Need a full question paper?

Generate a complete, print-ready paper with questions like this in minutes — across 16+ boards, with answer keys.

Start Generating Free

Similar questions

If speed of sound in air in $330 \,m / s$ then, find the number of tones present in an open organ pipe of length $1\, m$ whose frequency if $\leq 1000$.
A string in musical instrument is $50 cm$ long and its fundamental frequency is $800 Hz.$ If a frequency of $1000 Hz$ is to be produced, then required length of string is ..... $cm$
If Young's modulus of iron is $2 \times {10^{11}}\,N/{m^2}$ and the interatomic spacing between two molecules is $3 \times {10^{ - 10}}$metre, the interatomic force constant is ......... $N/m$
The de-Broglie wavelength associated with a particle of mass $m$ and energy $E$ is $\mathrm{h} / \sqrt{2 m E}$ The dimensional formula for Planck's constant is:
Ametal wire is clamped between two vertical walls.At $20 ^o C$ the unstrained length of the wire is exactly equal to the separation between walls. If the temperature of the wire is decreased the graph between elastic energy density $(u)$ and temperature $(T)$ of the wire is
Newton's law of cooling is used in laboratory for the determination of the
A ball is thrown up at an angle with the horizontal. Then, the total change of momentum by the instant it returns to the ground is
The moment of inertia of a solid cylinder about its axis is $I$. It is allowed to roll down an incline without slipping. If its angular velocity at the bottom be $\omega $, then $K.E.$ of the cylinder will be
Given below are two statement : one is labelled as Assertion $A$ and the other is labelled as Reason $R$.

Assertion $A$ : When a rod lying freely is heated, no thermal stress is developed in it.

Reason $R :$ On heating the length of the rod increases.

In the light of the above statements, choose the correct answer from the options given below

If $L = 2.331\,cm,\;B = 2.1\,cm$, then $L + B = $