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Quizzes (598) Questions (13441)

Questions Related to physics

Multiple choice resonance oscillations physics

Three simple harmonic motions in the same direction having the same amplitude a and same period are superposed. If each differs in phase from the next by $45^o$, then.

  1. The resultant amplitude $(1+\sqrt{2})a$

  2. The phase of the resultant motion relative to the first is $90^o$

  3. The energy associated with the resulting motion is $(3+2\sqrt{2})$ times the energy associated with any single motion

  4. The resulting motion is not simple harmonic
Reveal answer Fill a bubble to check yourself
A,C Correct answer
Explanation

Let $y _1=a\sin \left(\omega t-\cfrac {\pi}{4}\right)$
$y _2=a\sin (\omega t)$
$y _3=a\sin \left(\omega t+\cfrac {\pi}{4}\right)$
On super imposing, resulting SHM-
$y=a\left[\sin \left(\omega t-\cfrac{\pi}{4}\right)+\sin \omega t+\sin \left (\omega t+\cfrac {\pi}{4} \right)\right]$
$\implies y=a \left[2\sin \omega t\cos \cfrac {\pi}{4}+\sin \omega t\right]$
$\implies y=a(1+\sqrt {2})\sin \omega t$
$\therefore$ Resultant amplitude $=(1+\sqrt{2})a$
Also, $\cfrac {E _{resultant}}{E _{single}}=\left(\cfrac {A}{a}\right)^2$
$\implies \cfrac {E _{resultant}}{E _{single}}=(\sqrt{2}+1)^2$
$\implies \cfrac {E _{resultant}}{E _{single}}=(3+2\sqrt{2})$
$\therefore E _{resultant}=(3+2\sqrt{2})E _{single}$

Multiple choice resonance oscillations physics

The amplitude of damped oscillator becomes $\dfrac{1}{3}$ in $2\ s$. Its amplitude after $6\ s$ is $1/n$ times the original. The value of $n$ is ?

  1. $2^{3}$

  2. $3^{2}$

  3. $3^{1/2}$

  4. $3^{3}$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

The amplitude of a damped oscillator follows A(t) = A0 * exp(-bt). Given A(2) = A0 / 3, we have exp(-2b) = 1/3. For t = 6, A(6) = A0 * exp(-6b) = A0 * (exp(-2b))^3 = A0 * (1/3)^3 = A0 / 27. Thus, n = 27 = 3^3.

Multiple choice resonance oscillations physics

A cylindrical tube,open at one end and closed at the other,is acoustic unison with an external source of frequency held at the open end of the tube, in its fundamental note. Then:

  1. The displacement wave from the source gets reflected with a phase change of $ \pi $ at the closed end

  2. The pressure wave from the source get reflected without a phase change at the closed end

  3. The wave reflected from the closed end again gets reflected at the open end

  4. The wave reflected from the closed end does not suffer reflection at the open end
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

A cylindrical tube,open at one end and closed at the other,is acoustic unison with an external source of frequency held at the open end of the tube, in its fundamental note, then the displacement wave from the source gets reflected with a phase change of  $\pi $ at the closed end.

so the correct option is A.

Multiple choice resonance oscillations physics

For a certain organ pipe open at both ends, the successive resonance frequencies are obtained at $510, 680$ and $850\ Hz$. The velocity of sound in air is $340\ m/s$. The length of the pipe must be:

  1. $2\ m$

  2. $0.5\ m$

  3. $m$

  4. $0.25\ m$
Reveal answer Fill a bubble to check yourself
A Correct answer
Multiple choice resonance oscillations physics

Suggest one way by which rattling sound could be stopped.

  1. Rattling sound can be stopped by changing the speed of the vehicle.

  2. <span>Rattling sound can be stopped by changing the frequency of the vehicle.</span>

  3. <span>Rattling sound can be stopped by changing the&nbsp;vibration&nbsp;of the vehicle.</span>

  4. None of the above.
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The cause of rattling sound is resonance and it can be stopped by changing the speed of the vehicle. 

Multiple choice resonance oscillations physics

Some opera singers are able to use their voice to shatter a crystal glass. Which of the phenomenon is used to explain this ? 

  1. Acoustic reflection

  2. Multiple echoes

  3. Interference

  4. Resonance

  5. Beats
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

 When the  external frequency becomes equal to the natural frequency of the body , then the amplitude of vibrations of the body becomes very large , this phenomenon is called resonance .

   When a opera singer  manages his frequency such that it becomes equal to the natural frequency of crystal glass , resonance occurs and glass shatters.

Multiple choice resonance oscillations physics

Equations y = 2A cos$^{2}$ $\omega $t and y = A (sin $\omega $  + $\sqrt{3}$ cos $\omega $t  ) represent the motion of two particles.

  1. Only one of these is S.H.M.

  2. Ratio of maximum speeds is 2 : 1

  3. Ratio of maximum speeds is 1 : 1

  4. Ratio of maximum accelerations is 1 : 4
Reveal answer Fill a bubble to check yourself
C Correct answer
Multiple choice resonance oscillations physics

Your friend is playing a song on a piano. Whenever your friend hits a certain key, the lamp on top of the piano rattles. Explain why the lamp rattles.

  1. <span>The lamp rattles because of the occurring of interference&nbsp;</span>

  2. <span>The lamp rattles because of the occurring of&nbsp;diffraction&nbsp;</span>

  3. <span>The lamp rattles because of the occurring of resonance</span>

  4. None of the above&nbsp;
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

This happens due to resonance (A phenomenon in which a vibrating system or external force drives another system to oscillate with a greater amplitude at a specific frequency). The lamp on top of the piano has a resonant frequency equal to one of the notes being played.

Multiple choice resonance oscillations physics

During resonance, sound waves tend to absorb

  1. more energy

  2. less energy

  3. no energy

  4. infinite energy
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

System to absorb more energy when the frequency of its oscillations matches the system's natural frequency of vibration than it does at other frequencies.

Multiple choice resonance oscillations physics

A glass tube of $1.0 m$ length is filled with water. The water can be drained out slowly at bottom of the tube. If a vibrating turning fork of frequency $500 Hz$ is brought at the upper end of the tube and the velocity of sound is $330 \,\,m\,\,s^{-1}$, then the total number of resonances obtained will be:

  1. 4

  2. 3

  3. 2

  4. 1
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Wavelength of the sound produced is,
$\lambda = \dfrac{Velocity}{Frequency} $


$= \dfrac{330\,\,m\,\,s^{-1}}{500\,\,s^{-1}} = 0.66\,\,m$
The resonance occurs at
$\dfrac{\lambda}{4},\dfrac{3\lambda}{4},\dfrac{5\lambda}{4},\dfrac{7\lambda}{4},.....$
i.e., at $0.165\,\,m, 0.495\,\,m, 0.825\,\,m, 1.155\,\,m$. As the length of the tube is only $1.0\,\,m$, hence $3$ resonance will be observed.