question_answer

A dog barks in a park and hears its echo after 0.5 seconds. The sound of its bark got reflected by a nearby building. The sound of speed in air is 346 m/s. The distance between the dog and the building is

A)  86.5 m

B)  80.6 m           

C)  75 m              

D)  8.65 m

Correct Answer: A

Solution :

                    The echo is heard when the sound wave travels a distance \[2x\]. As \[\text{distance = speed }\times \text{ time}\] \[\therefore 2x=346\times 0.5\] Or \[x=\frac{346\times 0.5}{2}=86.5m\]