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A person, standing between two parallel hills, fires a gun. He hears the first echo after 1.5 s and the second after 2.5 s. If the speed of sound is 332 m/s, calculate the distance between the hills. When will he hear the third echo? |
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Answer» <P> Solution :LET the person P be at a distance x from hill `H_1 and y " from " H_2` as shown in figure. The time interval between the original sound and echoes from `H_1 and H_2` will be respectively. So the distance between the hills `x + y =v/2 (t_1+t_2) = 332/2 [1.5 +2.5] = 664 m` Now as I ECHO will be from `H_1` after TIMES `t_1` while II echo from `H_2` after time `t_2`, III echo will be produced due to reflection of sound of I echo from `H_2` or of II echo from `H_1`, i.e., `t_3 =t_1 +t_2 =1.5 +2.5 = 4 sec`i.e., III echo will be produced after 4 sec. and in it sound from both I and II echoes will reach simultaneously. |
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