Tag: study of sound

Questions Related to study of sound

An observer heard his echo $2.5$ seconds after he produced the sound by standing before a wall $400$ m away from him. The speed of sound in air is ____ m/s

physics study of sound determination of speed of sound by echo problems on sound sound needs a medium

  1. $320$

  2. $160$

  3. $330$

  4. $200$

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Correct Option: D

If d is the distance between the source of sound and reflector $t _1, t _2$ are times at which echoes are heard, the expression for determination of velocity of sound in air by echo method is :

physics study of sound determination of speed of sound by echo problems on sound sound needs a medium

  1. $\displaystyle \frac{2d}{t _2-t _1}$

  2. $\displaystyle \frac{2d}{t _1-t _2}$

  3. $\displaystyle \frac{4d}{t _1-t _2}$

  4. $\displaystyle \frac{2d}{t _1+t _2}$

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Correct Option: B
Explanation:

The speed of the sound, distance traveled and the time taken relationship if the sound is a reflected sound, that is echo, it is given as follows.
$Speed\; of \; sound=\dfrac { 2\times Distance\; traveled\; (m) }{ Time\; taken(s) } $.
In the question it is given that distance traveled by the sound from the source to the reflector is d and the time taken to hear the echo are $t _1$ and $t _2$ seconds.
The speed of the sound wave is calculated as follows.$v=\dfrac { 2d }{ t _1-t _2 } m/s$.

A man stands at a distance of $250m$ from a cliff. He  fires a gun and heard the echo after $1.5$ second . What will be the velocity of the second?

physics study of sound determination of speed of sound by echo problems on sound sound needs a medium

  1. $333.3m/s$

  2. $330m/s$

  3. $320m/s$

  4. $33.3m/s$

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Correct Option: C

A man stands at a distance of $225 m$ from a cliff. He fires a gun and heard the echo after $1.5 sec$. What will be the velocity of the sound?

physics study of sound determination of speed of sound by echo problems on sound sound needs a medium

  1. ${ 300ms }^{ -1 }$

  2. ${ 340ms }^{ -1 }$

  3. ${ 320 ms }^{ -1 }$

  4. ${ 335 ms }^{ -1 }$

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Correct Option: A
Explanation:

The echo is the sound reflection from a surface. Thus, total distance be covered by sound is $d=2\times 225=450 m$.

Using , $S=vt$, we get $v=d/t=450/1.5=300 m/s$

An echo returns in 30 s. What is the distance of the reflecting surface from the source? 

Given that speed of sound= 342m/s

physics study of sound determination of speed of sound by echo problems on sound sound needs a medium

  1. 5100 m

  2. 22.66m

  3. 5130 m

  4. 22.8 m

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Correct Option: C
Explanation:

Time taken by the wave to travel from the sound to the reflecting surface $= t = \dfrac{30}{2} = 15 m$
Speed $= 342 m/s$ 
Distance of reflecting surface from the sound $= 342 \times 15 = 5130 m$

A man standing in front of a large wall claps at a regular frequency of $10Hz$. He finds that the echoes coincide with his clapping. (The speed od sound in air is $330ms^{-1}.)$
(i) Time taken between successive clapping is $0.1s$.
(ii) The distance between the man and the wall, after he clapping, If he hears one more echo is $33m$.
(iii) The distance between the man and the wall, after he stops clapping, if he hears four more echoes is $66m$.

physics study of sound determination of speed of sound by echo problems on sound sound needs a medium

  1. Only (i) and (ii) are correct.

  2. Only (ii) and (iii) re correct.

  3. Only (i) and (iii) are correct.

  4. All (i), (ii) and (iii) are correct.

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Correct Option: A

A man fires a shot and hears an echo from a cliff after $2sec$. He walks $85m$ towards the cliff and the seconds shot is now heard after $1.5sec$. What is the distance o the man from the cliff when the first echo was heard.

physics study of sound determination of speed of sound by echo problems on sound sound needs a medium

  1. $170m$

  2. $340m$

  3. $510m$

  4. $680m$

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Correct Option: A

A boy clapped his hands near a cliff and heard the echo after 4s. What is the distance of the cliff from the person if the speed of the sound, v is taken as 346 ms$^{-1}$?

physics study of sound determination of speed of sound by echo problems on sound sound needs a medium

  1. 2 m

  2. 1384 m

  3. 692 m

  4. 2768 m

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Correct Option: C
Explanation:

Given, Speed of sound, $v = 346 ms^{-1}$ Time taken for hearing the echo, $t = 4 s$
Distance travelled by the sound $ = v \times t = 346 m/s \times 4 s = 1384 m$
In 4 s sound has to travel twice the distance between the cliff and the person.
Hence, the distance between the cliff and the person $= 1384 m/2 = 692 m$

A sound wave of wavelength $\lambda$ travels towards the right horizontally with a velocity V. It strikes and reflects from a vertical plane surface, travelling at a speed v towards the left. The number of positive crests striking during a time interval of three seconds on the wall is :

physics study of sound determination of speed of sound by echo problems on sound sound needs a medium

  1. $3(V+v)/\lambda$

  2. $3(V-v)/\lambda$

  3. $(V+v)/3\lambda$

  4. $(V-v)/3\lambda$

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Correct Option: A

A person is in front of a fort wall.  The person can hear an echo of sound produced by him when minimum distance between person and wall is 16.75 m. The velocity of sound in air is:

physics study of sound determination of speed of sound by echo problems on sound sound needs a medium

  1. 330 m/s

  2. 335 m/s

  3. 337.5 m/s

  4. 345 m/s

Show answer
Correct Option: B
Explanation:

Minimum time for echo is $0.15$
So, distance travelled for echo is $=2\times 16.75=$ speed of sound $\times$ minimum time for echo
$\Rightarrow 2\times 16.75=\vartheta _{s}\times 0.1$

$\Rightarrow \vartheta _{s}=\dfrac{2\times 16.75}{0.1}$$=335 m/s$