An engine approaches a hill with a constant speed. When it is at a distance of 0.9 km it blows a whi

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14.Waves and Sound

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An engine approaches a hill with a constant speed. When it is at a distance of $0.9 km$ it blows a whistle, whose echo is heard by the driver after $5$ sec. If speed of sound in air is $330 m/s$, the speed of engine is .... $m/s$

$10$

$20 $

$30$

$40 $

Solution

(c) If the speed of engine is v, the distance traveled by engine in $5$ sec will be $5v$, and hence the distance traveled by sound in reaching the hill and coming back to the moving driver $= 900 + (900 -5v) = 1800 -5v$

So the time interval between original sound and it’s echo $t = \frac{{(1800 – 5v)}}{{330}} = 5$ $==> v = 30 m/s.$

Standard 11

Physics

Equation of a plane progressive wave is given by $y = 0.6\, \sin 2\pi \left( {t – \frac{x}{2}} \right)$.On reflection from a denser medium its amplitude becomes $2/3$ of the amplitude of the incident wave. The equation of the reflected wave is :-

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The speed of sound in oxygen $(O_2)$ at a certain temperature is $460\, ms^{-1}$. The speed of sound in helium $(He)$ at the same temperature will be …………. $\mathrm{m/s}$ (assume both gases to be ideal)

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The length of open organ pipe is $L$ and fundamental frequency is $f$. Now it is immersed into water upto half of its length now the frequency of organ pipe will be

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Two trains $A$ and $B$ initially $120\, km$ apart, start moving towards each other on the same track with a velocity of $60\, km/hr$ each. At the moment of start $A$ blows a whistle, which reflects on $B$ and subsequently reflects from $A$ and so on. Take the velocity of sound waves in air $1200\, km/hr$. The distance travelled by sound waves before the trains crash will be (in $km$)

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If $L_1$ and $L_2$ are the lengths of the first and second resonating air columns in a resonance tube, then the wavelength of the note produced is

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An engine approaches a hill with a constant speed. When it is at a distance of $0.9 km$ it blows a whistle, whose echo is heard by the driver after $5$ sec. If speed of sound in air is $330 m/s$, the speed of engine is .... $m/s$

Solution

Similar Questions

Equation of a plane progressive wave is given by $y = 0.6\, \sin 2\pi \left( {t – \frac{x}{2}} \right)$.On reflection from a denser medium its amplitude becomes $2/3$ of the amplitude of the incident wave. The equation of the reflected wave is :-

The speed of sound in oxygen $(O_2)$ at a certain temperature is $460\, ms^{-1}$. The speed of sound in helium $(He)$ at the same temperature will be …………. $\mathrm{m/s}$ (assume both gases to be ideal)

The length of open organ pipe is $L$ and fundamental frequency is $f$. Now it is immersed into water upto half of its length now the frequency of organ pipe will be

If $L_1$ and $L_2$ are the lengths of the first and second resonating air columns in a resonance tube, then the wavelength of the note produced is

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