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InterviewSolution
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Two children are at opposite ends of an aluminium rod. One strikes the end of rod with a stone. Find the ratio of times taken by sound wave in air and in aluminium to reach the second child (Given: Speed of sound in air =346m//s, Speed of sound in aluminium = 6420m//s). |
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Answer» Solution :Suppose the length of aluminium ROD is l. Then the distance travelled by sound in aluminium as well as in air to reach the second child will be equal to l. (i) SPEED of sound (in air) `= ("Distance travelled in air")/("Time taken in air")` ltbgt or `346 = (l)/("Time taken in air")` And, Time taken in air `= (l)/(346)` ...(1) (ii) Speed of sound (in aluminium) `= ("Distance travelled in aluminium")/("Time taken in aluminium")` or `6420 = (l)/("Time taken in aluminium")` And, Time taken in aluminium `= (l)/(6420)` .....(2) Now, dividing equation (1) by equation (2) we get: `("Time taken by sound in air")/("Time taken by sound in aluminium") = (l)/(346) xx (6420)/(l)` Cancelling l from the right side, we get: `("Time taken by sound in air")/("Time taken by sound in aluminium") = (6420)/(346)` `= (18.55)/(1)` Thus, the ratio of times taken by the sound waves in air and in aluminium to reach the second child (by TRAVELLING the same distance) is 18.55:1. |
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