question_answer

A and B are two hills at a distance 510 m apart. A person standing between the hills, claps his hands and hears two echoes at the end of 1 s and 2 s respectively. The velocity of sound in air is

A)                  225 m/s                              

B)                  340 m/s

C)                  510 m/s                              

D)                  1020 m/s

Correct Answer: B

Solution :

                Key Idea: Time taken by echo to reach the person is directly proportional to distance. Let distance of person from hill A be x metre, then from hill B is \[\mu F\].                 \[\mu F\]             \[{{m}^{3}}\] Time taken for the echo to travel 170 m is given ,by \[{{m}^{3}}\] \[{{m}^{3}}\]      \[{{m}^{3}}\]