Advertisements
Advertisements
Question
A person standing between two vertical cliffs and is 640 m away from the nearest cliff. He shouted and heard the first echo after 45s and the second echo after further 3s. Calculate the speed of sound in air and the distance between the cliffs.
Solution
Given: d1 = 640m; t1 = 4s
t2 = 4 + 3 = 7
First echo is heard from the nearest cliff.
Total distance travelled = 2d = 2 × 640 = 1280 m
v = `(2"d"_1)/"t"_1=1280/4` = 320 m/s
Second echo is heard from the first cliff
v = `(2"d"_2)/"t"_2`
⇒ 320 ms−1 = `("2d"_2)/7`
d2 = `(320xx7)/2` = 1120 m
hence, the distance between two cliff
d1 + d2 = 640 + 1120 = 1760 m.
APPEARS IN
RELATED QUESTIONS
A radar sends a signal to an aircraft at a distance of 30 km away and receives it back after 2 x 10-4 seconds. What is the speed of the signal?
The wavelength of waves produces on the surface of water is 20 cm. If the wave velocity is 24 m s-1, calculate:
- the number of waves produced in one second, and
- the time in which one wave is produced.
Calculate the minimum distance in air required between the source of sound and the obstacle to hear an echo. Take speed of sound in air = 350 m s-1
A pendulum has a frequency of 4 vibrations per second. An oberver starts the pendulum and fires a gun simultaneously. He hears the echo from the cliff after 6 vibrations of the pendulum, if the velocity of sound in air is 340 m/s, find the distance betwen the cliff and the obsever.
An observer standing in front of a vertical wall claps 10 times one second. He adjusts his distance from the wall in such a way that the second of his clapping coincides with the echo. This happens when bis distance from the wall is 17.5m. What is the velocity of sound heard by him?
An observer stands at a distance of 850 m from a cliff and fires a gun. After what time gap will he hear the echo? If sound travels at a speed of 350 m/sec., in air.
An observer stands at a certain distance away from a cliff and produces a loud sound. He hears the echo of the sound after 1.8 s. Calculate the distance between the cliff and the observer if the velocity of sound in air is 340 m−1.
An instrument is able to detect the reflected waves from an enemy aeroplane, after a time interval of 0.02 milliseconds. If the velocity of the waves is 3 × 108 ms−1, calculate the distance of the plane from the radar.
A boy stands in from of a cliff on the other side of a river. He fires a gun and hears an echo after 6 seconds. The boy then moves backward by 170 m and again fires the gun. He hears an echo after 7 seconds. Calculate
(i) width of river,
(ii) speed of sound.
