Explain relative velocity.

The relative velocity of an object A with respect to another object B.

Explanation:

The relative velocity of an object A with respect to another object B is the velocity that object A would appear to have to an observer situated on object B moving along with it.

0.05773 sec

Explanation:

We know that

time = distance/speed = d/V

for air

t1 = 117/355 = 0.3295 sec

for fresh water

t_2 = 117/1480 = 0.07905 sec

for metal

t_3 = 117/5490 = 0.02131 sec

So as we can see sound will reach through metal hand rail 1st, then through fresh water and then through air

1st = metal hand rail

2nd = fresh water

3rd = air

time difference between 1st and 2nd sound = t_2 - t_3 = 0.07905 - 0.02131 = 0.05773 sec