A person, with his ear to the ground, sees a huge stone strike the concrete pavement. A moment later two sounds are heard from the impact: one travels in the air and the other in the concrete, and they are 0.50 s apart. The speed of sound in air is 343 m/s, and in concrete is 3000 m/s. Required:
How far away did the impact occur?

The distance is

Explanation:

From the question we are told that

   The time interval between the sounds is  k =  0.50 s

    The  speed of sound in air is  

    The  speed of sound in the concrete is

Generally the distance where the collision occurred is  mathematically represented as

Now from the question we see that d is the same for both sound waves

 So

Now  

So

=>    

=>    

=>    

So

explanation:

v=uf/(u-f)

= 5.-10/(5+10) convex lens has negative focal length

1/0.14nm = 10^10/1.4 a lot