Download App

Wave Motion and Waves on a String — Physics STD 12 Science — Question

Rajasthan BoardEnglish MediumSTD 12 SciencePhysicsWave Motion and Waves on a String3 Marks
Question
Figure, shows a string stretched by a block going over a pulley. The string vibrates in its tenth harmonic in unison with a particular tuning fork. When a beaker containing water is brought under the block so that the block is completely dipped into the beaker, the string vibrates in its eleventh harmonic. Find the density of the material of the block.
✓

Answer

Let, $\rho\rightarrow$ density of the block Weight $\rho\text{Vg}$ where V = volume of block The same turning fork resonates with the string in the two cases$\text{f}_{10}=\frac{10}{2\text{l}}\sqrt{\frac{\text{T}-\rho_\text{w}\text{Vg}}{\text{m}}}=\frac{11}{2\text{l}}\sqrt{\frac{(\rho-\rho_\text{w})\text{Vg}}{\text{m}}}$
As the f of tuning fork is same,$\text{f}_{10}=\text{f}_{11}\Rightarrow\frac{10}{2\text{l}}\sqrt{\frac{\rho\text{Vg}}{\text{m}}}=\frac{11}{2\text{l}}\sqrt{\frac{(\rho-\rho_\text{w})\text{Vg}}{\text{m}}}$
$\Rightarrow\frac{10}{11}=\sqrt{\frac{\rho-\rho_\text{w}}{\text{m}}}$
$\Rightarrow\frac{\rho-1}{\rho}=\frac{100}{121}$ $\big($because, $\rho_\text{w}=1\text{gm/cc}\big)$
$\Rightarrow100\rho=121\rho-121$
$\Rightarrow5.8\times10^{3}\text{kg/m}^3$

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

Explore more

More "3 Marks Question" from Wave Motion and Waves on a String→Wave Motion and Waves on a String — all question types→Physics STD 12 Science question papers→Rajasthan Board STD 12 Science question papers→Rajasthan Board question paper generator→

Similar questions

  1. Identify the part of the electromagnetic spectrum which is:
  1. Suitable for radar system used in aircraft navigation,
  2. Produced by bombarding a metal target by high-speed electrons.
  1. Why does a galvanometer show a momentary deflection at the time of charging or discharging a capacitor? Write the necessary expression to explain this observation.
→
Consider the situation shown in figure Show that if the blocks are displaced slightly in opposite directions and released, they will execute simple harmonic motion. Calculate the time period.
→
State the Lenz's law regarding electromagnetic induction. This law is based on the conservation law of which quantity?
A horizontal conducting wire of length 2 m oriented in east-west direction is falling down with a speed of 5 m/s perpendicular to the horizontal component of earth's magnetic field of $0.3 \times 10^{-4} T.$ Calculate the instantaneous value of induced emf across the ends of the wire.
→
Power factor of a coil in an ac circuit at 60 hertz frequency is 0.707 . If frequency of ac source becomes 120 hertz, then what will be power factor?
→
An inductor $\text{L}$ of inductance $\text{XL}$ is connected in series with a bulb $\text{B}$ and an ac source. How would brightness of the bulb change when $\text{(i)}$ number of turns in the inductor is reduced$, \text{(ii)}$ an iron rod is inserted in the inductor and $\text{(iii)}$ a capacitor of reactance $\text{X}_\text{C} = \text{X}_\text{L}$ is inserted in series in the circuit. Justify your answer in each case.
→
Mention any three applications of the internet. Explain one of these in detail.
→
Explain the de-Broglie wavelength by explaining the waveform of matter.
→
With the help of a simple diagram, explain the working of a silicon solar cell, giving all three basic processes involved. Draw its $I-V$ characteristic.
→
In a typical Indian Bugghi $($a luxury cart drawn by horses$),$ a wooden plate is fixed on the rear on which one person can sit. A bugghi of mass $200\ kg$ is moving at a speed of $10\ km/h$. As it overtakes a school boy walking at a speed of $4\ km/h,$ the boy sits on the wooden plate. If the mass of the boy is $25\ kg,$ what will be the new velocity of the bugghi?
→
Equal masses of air are sealed in two vessels, one of volume $V_0$ and the other of volume $2V_0.$ If the first vessel is maintained at a temperature $300K$ and the other at $600K,$ find the ratio of the pressures in the two vessels.
→