Tag: physics

Questions Related to physics

Which of the following is an example of oscillatory motion? 

physics sound: production of sound oscillation - amplitude, time period and frequency of oscillation time period, frequency and amplitude of sound oscillatory and periodic motion

  1. Heart beat of a persion

  2. Motion of earth around the sun

  3. Motion of Hally's comet around the sun

  4. Oscillations of a simple pendulam

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Correct Option: D
Explanation:

Oscillation of a simple pendulum is a simple harmonic motion.

The displacement of a particle is represented by the equation $y=sin^3(\omega t)$. The motion is 

physics sound: production of sound oscillation - amplitude, time period and frequency of oscillation time period, frequency and amplitude of sound oscillatory and periodic motion

  1. non-periodic

  2. periodic but not simple harmonic

  3. simple harmonic with period $\dfrac{2 \pi}{\omega}$

  4. simple harmonic with period $\dfrac{\pi}{\omega}$

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Correct Option: B
Explanation:

Given the equation of displacement of the particle, $y={ sin }^{ 3 }\omega t$

We know $sin3\theta =3sin\theta -4{ sin }^{ 3 }\theta $
Hence, $y=\frac { (3sin\omega t-4sin3\omega t) }{ 4 } \ \Rightarrow 4\frac { dy }{ dt } =3\omega cos\omega t-4\times [3\omega cos3\omega t]\ \Rightarrow 4\times \frac { { d }^{ 2 }y }{ { dt }^{ 2 } } =-3{ \omega  }^{ 2 }sin\omega t+12\omega sin3\omega t\ \Rightarrow \frac { { d }^{ 2 }y }{ { dt }^{ 2 } } =\frac { -3{ \omega  }^{ 2 }sin\omega t+12\omega sin3\omega t }{ 4 } \ \Rightarrow \frac { { d }^{ 2 }y }{ { dt }^{ 2 } } $ is not proportional to y. 
Hence, the motion is not SHM. 
As the expression is involving sine function, hence it will be periodic. 
Also ${ sin }^{ 3 }\omega t={ \left( sin\omega t \right)  }^{ 3 }\ ={ [sin(\omega t+2\pi )] }^{ 3 }\ ={ [sin(\omega t+2\pi /\omega )] }^{ 3 }$
Hence, $y={ sin }^{ 3 }\omega t$ represents a periodic motion with period $2\pi /\omega $.

A horizontal plank has a rectangular block placed on it. The plank starts oscillating vertically and simple harmonically with an amplitude of 40 cm. The block just loses contact with the plank when the later is momentarily at rest. Then

physics sound: production of sound oscillation - amplitude, time period and frequency of oscillation time period, frequency and amplitude of sound oscillatory and periodic motion

  1. the period of oscillation is $2\pi /5\ s$

  2. the block weighs double its weight when the plank is at one of the positions of momentary at rest

  3. the block weighs 1.5 times its weight on the plank half way down

  4. the block weighs its true weight on the plank, when the latter moves fast

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Correct Option: B

In an electronic watch, the component corresponding to the pendulum of a pendulum clock is a__?

physics sound: production of sound oscillation - amplitude, time period and frequency of oscillation time period, frequency and amplitude of sound oscillatory and periodic motion

  1. Diode

  2. Transistor

  3. Crystal oscillator

  4. Balance wheel

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Correct Option: C

An oscillator is producing FM waves of frequency 2kHz with avariation of 10kHz. The modulating index=?

physics sound: production of sound oscillation - amplitude, time period and frequency of oscillation time period, frequency and amplitude of sound oscillatory and periodic motion

  1. 0.20

  2. 5.0

  3. 0.67

  4. 1.5

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Correct Option: B
Explanation:

Modulation Index , $m _f=\dfrac{\text{Maximum frequency deviation}}{\text{Modulating frequency}}$

$\Rightarrow m _f= \dfrac{10 kHz}{2 kHz}$
$\Rightarrow m _f=5$

Which one of the following will take place when a watch based on oscillating spring is taken to a deep mine?

physics sound: production of sound oscillation - amplitude, time period and frequency of oscillation time period, frequency and amplitude of sound oscillatory and periodic motion

  1. It will indicate the same time  on earth

  2. It will become fast

  3. It will become slow

  4. It will stop working

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Correct Option: A

A simple harmonic oscillator of angular frequency 2 rad $s^{-1}$ is acted upon by an external force $F= sin tN.$ If the oscillator is at rest in its equilibrium position at t=0, its position at later times is proportional to 

physics sound: production of sound oscillation - amplitude, time period and frequency of oscillation time period, frequency and amplitude of sound oscillatory and periodic motion

  1. $ sin t+ \frac{1}{2}cos 2t$

  2. $ cos t -\frac{1}{2}sin2t$

  3. $sint -\frac{1}{2}sin2t$

  4. $sin t +\frac{1}{2}sin 2t$

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Correct Option: C
Explanation:

The solution contains term proportional to $sin t$, $sin 2t$ & the only option consistent with initial conditions is (C)

Barometer was constructed by

physics pressure pressure in air introduction to atmospheric pressure devices to measure pressure

  1. Vermicelli

  2. Torricelli

  3. Archimedes

  4. Newton

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Correct Option: B
Explanation:

Barometer is a device used to measure atmospheric pressure. It was first constructed by Torricellli in the year 1643.

At sea level, the vertical height of mercury supported in the tube of simple barometer is ______ $cm$ above the mercury level in the bowl.
physics pressure in fluids and atmospheric pressure pressure in air introduction to atmospheric pressure devices to measure pressure

  1. $36$

  2. $76$

  3. $100$

  4. $7$

Show answer
Correct Option: B
Explanation:

The height to which mercury rises in simple barometer is $76cm$.

This is the reason that  atmospheric pressure is often expressed as $76cm$ of Hg at sea level.

Length of glass tube in simple barometer is
physics pressure in fluids and atmospheric pressure pressure in air introduction to atmospheric pressure devices to measure pressure

  1. $100\,mm$

  2. $1\,cm$

  3. $100\,cm$

  4. $1\,mm$

Show answer
Correct Option: C
Explanation:

A mercury barometer has a glass tube, of length approximately 100cm, closed at one end with an open mercury-filled reservoir at the base.