Tag: oscillatory and periodic motion

Questions Related to oscillatory and periodic motion

Two trains A and B are approaching each other with $108 km {h}^{-1}$ and $126 kg {h}^{-1}$ respectively. If the train 'A' sounds a whistle of frequency 500 Hz, find the frequency of the whistle as heard by a passenger in the train 'B'.

(a) before the trains cross each other and

(b) after the trains cross each other. (Take velocity of sound as $330 {ms}^{-1}$)

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. 608 Hz, 410 Hz

  2. 410 Hz, 608 Hz

  3. 330 Hz, 550 Hz

  4. 310 Hz, 660 Hz

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Correct Option: A

In an open pipe pressure at the ends of the pipe 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. minimum

  2. maximum

  3. zero

  4. depending on temperature, it can be maximum or minimum.

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Correct Option: A

If a vibrator strikes the water $50$ times in $5s$, then the frequency of wave 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. $10 Hz$

  2. $0.5 Hz$

  3. $5 Hz$

  4. $0.1 Hz$

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Correct Option: A
Explanation:
Total number of vibrations, in $5s$ is $50$.
So, number of vibrations in $1s$ is $\dfrac{50}{5}=10$
Frequency$=10Hz$

A source of wave produce 1 crest and 1 trough in 16s. Find the frequency of the wave.

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. .0625 Hz

  2. 16 Hz

  3. 100

  4. 0Hz

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Correct Option: A
Explanation:

No of crest 1, trough = 1
$Time = 16 s$
No of wave in $1s = 1/16 = 0.0625 \ Hz$

A human heart on an average beat 72 times a minute. Calculate its frequency

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. $72s^{-1}$

  2. $1.2s^{-1}$

  3. $4320s^{-1}$

  4. None

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Correct Option: B
Explanation:

No of beat = $72 min^{-1}$ = $\dfrac {72}{1min} = \dfrac {72}{60}$=$1.2s^{-1}$
Frequency = $1.2s^{-1}$

One sound wave strikes a person's ear every $1/100$ of a second. The speed of sound where the person is located is $345 m/s$.
What is the frequency of the sound?

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. $3.45\ Hz$

  2. $34,500\ Hz$

  3. $0.01\ Hz$

  4. $100\ Hz$

  5. $2.9\ Hz$

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Correct Option: D
Explanation:

Time period of sound wave       $T = \dfrac{1}{100}$ second


$\therefore$ Frequency of sound wave      $\nu = \dfrac{1}{T} =100$  $Hz$

If you go on increasing the stretching force on a wire in a guitar, its frequency

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. Increases

  2. Decreases

  3. Remains unchanged

  4. None of the above

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Correct Option: A
Explanation:

When a stretching force is applied to a string or a wire, it applies a restoring force in the opposite direction. This force tends to bring the wire in its original length. It is known as tension in wire.

When we apply a stretching force on the wire of a guitar, the wire applies tension backwards. Greater the stretching force, greater is the tension.
The frequency of vibration of a stretched wire is directly proportional to the square root of the tension in it.
Hence on increasing the stretching force on a wire in a guitar, its frequency increases

The sounds having frequency of $20$ Hz to $20,000$ Hz are

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. Ultrasound

  2. Infrasonics

  3. Hypersonics

  4. Audible Sounds

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Correct Option: D
Explanation:

In the case of sound waves, having frequency in between $20$ Hz and $20,000$ Hz, called audible sound and  waves of frequency smaller than $20$ Hz are called infrasonic and waves having frequency greater then $20,000$ Hz, called Hypersonics sounds.

The time taken by a particle in reaching from a trough to its next crest in a transverse wave 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. T/4

  2. T/2

  3. T

  4. 3T/4

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Correct Option: B
Explanation:

A crest and a trough are separated by a distance of $\lambda/2$. A distance of $\lambda/2$ corresponds to a time difference of T/2

The equation of motion of a particle is $x = a cos(\alpha t)^2$. 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. periodic but not oscillatory

  2. periodic and oscillatory

  3. oscillatory but not periodic

  4. neither periodic nor oscillatory.

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Correct Option: C
Explanation:

The motion is oscillatory but not periodic because the oscillations are followed from the maximum displacement (negative extreme) at t=0, the corresponding echo is equal to π/2