A boy sitting on a swing which is moving to an angle of $30^{\circ}$ from the vertical is blowing a whistle which is of frequency $1000 H z$ . The whistle is $2 m$ from the point of support of the swing. If a girl stands in front of the swing, the maximum and minimum frequencies she will hear are
(velocity of sound $= 330 m / s$ , $g = 9.8 m / s^{2}$ )

$1000, 990 H z$

$1007, 1000 H z$

$1007, 993 H z$

$1100, 900 H z$

Video Solution

Text Solution

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The correct Answer is:C

$h = l - l cos θ = [1 - cos θ]$
$p . E_{A} = k E_{B} \Rightarrow m g h = \frac{1}{2} m v^{2}$
$\Rightarrow V_{s} = \sqrt{2 g h} = \sqrt{2 g l (1 - cos θ)}$
$n_{max} = n [\frac{V}{V - V_{S}}]$ $n_{min} = n [\frac{V}{V + V_{S}}]$

Updated on:21/07/2023

Class 11 PHYSICS TRAVELLING WAVES

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Question 1 - Select One
A source on a swing which is covering an angle $θ$ from the vertical is producing a frequency $v$ . The source is distant $d$ from the place of support of swing. If velocity of sound is $c$ , acceleration due to gravity is $g$ . then the maximum and minimum frequency hearfd by a listener in froun of swing is

A $\frac{c v}{\sqrt{2 g d - c}}, \frac{c v}{\sqrt{2 g d + c}}$
B $\frac{c v}{\sqrt{2 g d (1 - cos θ)} - c}, \frac{c v}{\sqrt{2 g d (1 - cos θ)} + c}$
C $\frac{c v}{c - \sqrt{2 g d (1 - cos θ)}}, \frac{c v}{c + \sqrt{2 g d (1 - cos θ)}}$
D $\frac{c v}{c - \sqrt{2 g d (1 - sin θ)}}, \frac{c v}{c + \sqrt{2 g d (1 - sin θ)}}$
Question 1 - Select One
A train is travelling at $120 k m p h$ and blows a whistle of frequency $1000 H z$ . The frequency of the note heard by a stationary observer if the train is approaching him and moving away from him are (Velocity of sound in air $= 330 = m s^{- 1}$ )
A $1112 H z$ , $908 H z$
B $908 H z$ , $1112 H z$
C $1080 H z$ , $820 H z$
D $820 H z$ , $1080 H z$
Question 1 - Select One
A whistle of frequency 500 Hz tied to the end of a string of length 1.2 m revolves at 400 rev / min . A listener standing some distance away in the plane of rotation of whistle hears frequencies in the range (speed of sound = 340 m / s )
A436 to 574
B426 to 586
C426 to 574
D. 436 to 586
Question 1 - Select One
Two passenger trains moving with a speed of $108 k m / h o u r$ cross each other. One of them blows a whistle whose frequency is $750 H z$ . If sound speed is $330 m / s$ , then passengers sitting in the other train, after trains cross each other they will hear sound whose frequency will be
A $900 H z$
B $625 H z$
C $750 H z$
D $800 H z$
Question 1 - Select One
A whistle of frequency 500 Hz tied to the end of a string of length 1.2 m revolves at 400 rev / min . A listener standing some distance away in the plane of rotation of whistle hears frequencies in the range (speed of sound = 340 m / s )
A436 to 586
B426 to 574
C426 to 584
D436 to 674
Question 1 - Select One
A man holding a sound source at the top of a tower emitting frequency of sound as $v = 1000 H z$ . Suddenly it slips from his hand and falls down with $' g'$ acceleration. The frequency of sound heard by the man at $t = 4 sec$ . (Velocity of sound $= 320 m / s$ , $g = 10 m / s^{2}$ )
A $860 H z$
B $888 H z$
C $894.75 H z$
D $930 H z$
Question 1 - Select One
The frequency of a whistle of an engine is 600 cycles / sec is moving with the speed of 30 m / sec towards an observer. The apparent frequency will be (velocity of sound = 330 m / s )
A600 cps
B660 cps
C990 cps
D330 cps

The correct Answer is:C

$h = l - l cos θ = [1 - cos θ]$
$p . E_{A} = k E_{B} \Rightarrow m g h = \frac{1}{2} m v^{2}$
$\Rightarrow V_{s} = \sqrt{2 g h} = \sqrt{2 g l (1 - cos θ)}$
$n_{max} = n [\frac{V}{V - V_{S}}]$ $n_{min} = n [\frac{V}{V + V_{S}}]$

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Knowledge Check

A train is travelling at $120 k m p h$ and blows a whistle of frequency $1000 H z$ . The frequency of the note heard by a stationary observer if the train is approaching him and moving away from him are (Velocity of sound in air $= 330 = m s^{- 1}$ )

A whistle of frequency 500 Hz tied to the end of a string of length 1.2 m revolves at 400 rev / min . A listener standing some distance away in the plane of rotation of whistle hears frequencies in the range (speed of sound = 340 m / s )

Two passenger trains moving with a speed of $108 k m / h o u r$ cross each other. One of them blows a whistle whose frequency is $750 H z$ . If sound speed is $330 m / s$ , then passengers sitting in the other train, after trains cross each other they will hear sound whose frequency will be

A whistle of frequency 500 Hz tied to the end of a string of length 1.2 m revolves at 400 rev / min . A listener standing some distance away in the plane of rotation of whistle hears frequencies in the range (speed of sound = 340 m / s )

A man holding a sound source at the top of a tower emitting frequency of sound as $v = 1000 H z$ . Suddenly it slips from his hand and falls down with $' g'$ acceleration. The frequency of sound heard by the man at $t = 4 sec$ . (Velocity of sound $= 320 m / s$ , $g = 10 m / s^{2}$ )

The frequency of a whistle of an engine is 600 cycles / sec is moving with the speed of 30 m / sec towards an observer. The apparent frequency will be (velocity of sound = 330 m / s )

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NARAYNA-WAVES-Exercise-I (H.W)

The correct Answer is:C

h=l−lcosθ=[1−cosθ] p.EA=kEB⇒mgh=12mv2 ⇒Vs=√2gh=√2gl(1−cosθ) nmax=n[VV−VS] nmin=n[VV+VS]

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A source on a swing which is covering an angle θ from the vertical is producing a frequency v. The source is distant d from the place of support of swing. If velocity of sound is c, acceleration due to gravity is g. then the maximum and minimum frequency hearfd by a listener in froun of swing is

A train is travelling at 120kmph and blows a whistle of frequency 1000Hz . The frequency of the note heard by a stationary observer if the train is approaching him and moving away from him are (Velocity of sound in air =330=ms−1)

A whistle of frequency 500 Hz tied to the end of a string of length 1.2 m revolves at 400 rev / min . A listener standing some distance away in the plane of rotation of whistle hears frequencies in the range (speed of sound = 340 m / s )

Two passenger trains moving with a speed of 108km/hour cross each other. One of them blows a whistle whose frequency is 750Hz. If sound speed is 330m/s, then passengers sitting in the other train, after trains cross each other they will hear sound whose frequency will be

A whistle of frequency 500 Hz tied to the end of a string of length 1.2 m revolves at 400 rev / min . A listener standing some distance away in the plane of rotation of whistle hears frequencies in the range (speed of sound = 340 m / s )

A man holding a sound source at the top of a tower emitting frequency of sound as v=1000Hz. Suddenly it slips from his hand and falls down with 'g' acceleration. The frequency of sound heard by the man at t=4sec. (Velocity of sound =320m/s, g=10m/s2)

The frequency of a whistle of an engine is 600 cycles / sec is moving with the speed of 30 m / sec towards an observer. The apparent frequency will be (velocity of sound = 330 m / s )

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NARAYNA-WAVES-Exercise-I (H.W)

$h = l - l cos θ = [1 - cos θ]$
$p . E_{A} = k E_{B} \Rightarrow m g h = \frac{1}{2} m v^{2}$
$\Rightarrow V_{s} = \sqrt{2 g h} = \sqrt{2 g l (1 - cos θ)}$
$n_{max} = n [\frac{V}{V - V_{S}}]$ $n_{min} = n [\frac{V}{V + V_{S}}]$

A train is travelling at $120 k m p h$ and blows a whistle of frequency $1000 H z$ . The frequency of the note heard by a stationary observer if the train is approaching him and moving away from him are (Velocity of sound in air $= 330 = m s^{- 1}$ )

Two passenger trains moving with a speed of $108 k m / h o u r$ cross each other. One of them blows a whistle whose frequency is $750 H z$ . If sound speed is $330 m / s$ , then passengers sitting in the other train, after trains cross each other they will hear sound whose frequency will be

A man holding a sound source at the top of a tower emitting frequency of sound as $v = 1000 H z$ . Suddenly it slips from his hand and falls down with $' g'$ acceleration. The frequency of sound heard by the man at $t = 4 sec$ . (Velocity of sound $= 320 m / s$ , $g = 10 m / s^{2}$ )