Question

Elwin is standing 50.0m from a large bell. He throws a rock at the bell and hears the sound of the bell 4.50s later. If the speed of sound is 330m/s, what was the speed of the rock?

Answer 1

Time taken by the sound to come from bell to Elwin

$t = \frac{d}{v}$

here we know that

d = 50 m

v = 330 m/s

now from above equation we have

$t_1 = \frac{50}{330} = 0.15 s$

now since we know that total time taken to hear the sound is 4.50s

so here we will have time to reach the rock to the bell is

$t_2 = t - t_1$

$t_2 = 4.50 - 0.15 = 4.35 s$

now we know that distance of the bell is 50 m

so speed of the rock is given as

$v = \frac{d}{t_2} = \frac{50}{4.35}$

$v = 11.5 m/s$