question_answer

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

A)  86.5 m     

B)  86 m

C)  85 m                                    

D)  75 m

Correct Answer: A

Solution :

  Let the distance of the dog from the building = d. The distance travelled by sound in 0.5s is 2d. We know, \[s=vt\] \[\Rightarrow \] \[2d=vt\] \[\Rightarrow \]\[d=\frac{vt}{2}=\frac{346\times 0.5}{2}m\]                 \[=86.5\text{ }m\]