Physics

Oscillations and Periodic Motion

162 Questions

Oscillations and periodic motion describe the movement of objects repeating their paths in regular intervals. Key concepts include simple pendulums, kinetic energy variations, and mechanical resonance. This physics topic is vital for various competitive exams.

Simple pendulumTime period calculationsKinetic energy in SHMMechanical resonanceDamped oscillations

Oscillations and Periodic Motion Questions

Multiple choice uniform magnetic field lines of earth magnetism physics

With a standard rectangular bar magnet, the time period in a vibration magneto meter is $4\  sec.$ The bar magnet is cut parallel to its length into $4$ equal pieces. The time period in vibration magnetometer when the piece is used $($in sec$) ($bar magnet breadth is small$)$            

  1. $16$
  2. $8$
  3. $4$
  4. $2$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Time period of vibration: $T \propto \sqrt{\dfrac{I}{M}}$ where $I$ is the moment of inertia and $M$ is the magnetic moment
$ \therefore$ $\dfrac{T _1}{T _2}= \sqrt{\dfrac{I _1M _2}{I _2M _1}}$
When the magnet is cut into 4 pieces parallel to its length, magnetic moment remains same since the breadth is very small..
$\therefore M _1= M _2$
Moment of inertial also  does not change.
$I _2=I _1$
$ \therefore \dfrac{T _1}{T _2}=\sqrt{\dfrac{I _1M _2}{I _2\times M _1}}=1$
$ \therefore T _2 = T _1=4$

Multiple choice uniform magnetic field lines of earth magnetism physics

With a standard rectangular bar magnet 'the time period of a vibration magnetometer is $4 s$. The bar magnet is cut parallel to its length into four equal pieces. The time period of vibration magnetometer when one piece is used (in second) (bar magnet breadth is, small) is

  1. $16$
  2. $8$
  3. $4$
  4. $2$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Time period of magnet, $T=2\pi \sqrt { \dfrac { I }{ MB }  } $
When magnet is cut parallel to its length into four equal pieces.
Then new
magnetic moment, ${ M }^{ \prime  }=\dfrac { M }{ 4 } $
New moment of inertia, ${ I }^{ \prime  }=\dfrac { I }{ 4 } $
$\therefore $ New time period, ${ T }^{ \prime  }=2\pi \sqrt { \dfrac { { I }^{ \prime  } }{ { M }^{ \prime  }{ B }^{ \prime  } }  } $
$\Rightarrow \quad T={ T }^{ \prime  }=4s$

Multiple choice physics motion of system of particles and rigid bodies centre of gravity turning effects of forces forces - vectors and moments

In an artificial satellite, the use of a pendulum watch is discarded, because :

  1. The satellite is in a constant state of motion
  2. The effective value of $g$ becomes zero in the artificial satellite

  3. The periodic time of the pendulum watch is reduced

  4. None of these
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

A pendulum watch relies on gravity to oscillate. Inside an orbiting satellite, objects are in a state of free fall, meaning the effective gravitational acceleration (g) is zero, causing the pendulum to stop oscillating.

Multiple choice audible, infra and ultra sound with its application study of sound physics

A vibrating body produces sound. However no sound is heard when a simple pendulum oscillates in air. Why?

  1. Frequency of vibration of pendulum is very high.

  2. Frequency of vibration of pendulum is more than 20 Hz

  3. Frequency of vibration of pendulum is less than 20 Hz

  4. Frequency of vibration of pendulum is exactly equal to 20 Hz.
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Sound is heard only if the body vibrates with a frequency of at least 20 Hz. Frequency of vibration of the pendulum is less than 20 Hz. Hence no sound is heard when the pendulum vibrates or oscillates in air.

Multiple choice audible, infra and ultra sound with its application study of sound physics

A pendulum vibrates with a time period of 1 second. What kind of sound is produced by it?

  1. Supersonic

  2. Audible

  3. Infrasonic

  4. Ultrasonic
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

The low frequency vibration of infrasonic wave is less than $20\,Hz$. The pendulum vibrates at this low frequency with a time period of $1$ second.

Multiple choice evs atmosphere- wind weather, climate and adaptation of animals to different climates climate and weather weather, climate and adaptations of animals to climate

An ordinary clock loses time in summer. This is because

  1. The length of the pendulum increases and time period increases

  2. The length of the pendulum increases and time period decreases

  3. The length of the pendulum decreases and time period increases

  4. The length of the pendulum decreases and time period decreases
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

As temperature increases in summer, the metal pendulum rod undergoes thermal expansion, increasing its length. Since the period of a pendulum is proportional to the square root of its length, a longer pendulum results in a longer time period, causing the clock to run slow.

Multiple choice physics the essence of change different forms of energy energy conversions energy transformations and energy transfers

A pendulum rocks back and forth. In an ideal setting, this motion would go on perpetually without loss of mechanical energy. Realistically, if you held a pendulum up and made it go in motion, it would slow to a stop.
What is responsible for the pendulum gradually losing mechanical energy? Ignore the mass of the string holding the pendulum bob in motion.

  1. The work done by gravity

  2. The work done by tension

  3. The work done by air resistance

  4. The pendulum does not lose mechanical energy

  5. There is not enough information to determine the cause
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

The vibrations of the pendulum die after some time , it is because of the frictional force of air which opposes the motion of bob .So air resistance is responsible for the loss in mechanical energy .

Multiple choice evs artificial satellite types of artificial satellites geostationary orbits moon and stars in sky

Time period of a simple pendulum inside a satellite orbiting earth is

  1. Zero
  2. $\infty$
  3. $T$
  4. $2T$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

As we know, $T\alpha \dfrac { 1 }{ \sqrt { g }  } $

On a artificial satellite, orbiting the earth, neg gravity is zero. As,
$\Rightarrow \quad g=0\Rightarrow T\rightarrow \infty $
$\Rightarrow$  Option B is the correct answer.

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

The time period of a vibrating body is $0.01\;sec$. Its frequency will be :

  1. $1.0\;s^{-1}$
  2. $10.0\;s^{-1}$
  3. $100.0\;s^{-1}$
  4. $1000.0\;s^{-1}$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Given,


Time period $=0.01\,sec$

We have to find the frequency

We have the relation,

$Frequency=\frac{1}{Time\,Period}$

That is,

$Frequency=\frac{1}{0.01}=100\,s^{-1}$

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

The average speed of the to bob of a seconds pendulum is $2 {ms}^{-1}$. Determine the frequency of oscillation.

  1. 0.5 Hz

  2. 1.5 Hz

  3. 0.9 Hz

  4. 2 Hz
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

For a pendulum, average speed = total distance / total time. In one oscillation, the bob travels 4A distance in time T. Average speed = 4A / T = 4Af. Given average speed = 2 m/s and length of a seconds pendulum is 1m (T=2s), we find the frequency.

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

What is the number of degrees of freedom of an oscillating simple pendulum?

  1. more than three

  2. 3

  3. 2

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

There are 2 degrees of freedom, 1 translational along which the pendulum bob moves, and second rotational - the hinge about which it forms an arc motion.

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

An object swinging on the end of a string forms a simple pendulum. Some students (and some texts) often cite the simple pendulum's motion as an example of SHM. That is not quite accurate because the motion is really

  1. approximately SHM only for small amplitudes

  2. exactly SHM only for amplitudes that are smaller than a certain value

  3. approximately SHM for all amplitudes.

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

An object performing SHM moves along a straight path.

For large amplitudes, a pendulum moves in a curved path.

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

Which of  the  following regarding oscillatory motion is true?

  1. Motion of the earth is periodic but not oscillatory because it is not to and fro.

  2. Quivering of the string of the musical instrument is an example of oscillatory motion

  3. Motion of the earth is periodic and oscillatory motion because it is not to and fro.

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

Oscillator motion is to and fro motion about a mean position. Earth motion is not a to and fro motion here, hence it is not an oscillatory motion. But as earth motion is repeated in a regular interval of time, its motion is periodic.

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

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

  1. Diode

  2. Transistor

  3. Crystal oscillator

  4. Balance wheel
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Electronic watches use a quartz crystal oscillator to provide a stable frequency for timekeeping, replacing the mechanical pendulum or balance wheel.