A motor car moving away from a cliff with a velocity of 90 kmph sounds the horn and the echo is heard after 20 seconds. Assuming the velocity of sound in air to be 335 ms $^{- 1}$ , the distance between the car and cliff when the horn is sounded is

3100m

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3580m

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3590m

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3560m

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Solution

The correct option is A 3100m
$ϑ a = 90 k m / h$

$= 90 \times \frac{1000}{3600} m / s$
$= 25 m / s$
So, here distance travelled by sound waves for echo is:
$2 x + ϑ$ (time of echo) $=$ speed of sound $\times$ time of echo
$2 x + 25 (20) = 335 \times 20$
$2 x = 6200$
$x = 3100 m$

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A motor car moving away from a cliff with a velocity of 90 kmph sounds the horn and the echo is heard after 20 seconds. Assuming the velocity of sound in air to be 335 ms−1, the distance between the car and cliff when the horn is sounded is

The correct option is A 3100mϑa=90 km/h =90×10003600 m/s =25 m/sSo, here distance travelled by sound waves for echo is:2x+ϑ (time of echo) = speed of sound × time of echo2x+25(20)=335×202x=6200x=3100 m

A motor car moving away from a cliff with a velocity of 90 kmph sounds the horn and the echo is heard after 20 seconds. Assuming the velocity of sound in air to be 335 ms $^{- 1}$ , the distance between the car and cliff when the horn is sounded is

The correct option is A 3100m
$ϑ a = 90 k m / h$

$= 90 \times \frac{1000}{3600} m / s$
$= 25 m / s$
So, here distance travelled by sound waves for echo is:
$2 x + ϑ$ (time of echo) $=$ speed of sound $\times$ time of echo
$2 x + 25 (20) = 335 \times 20$
$2 x = 6200$
$x = 3100 m$