A rock thrown horizontally at a large bell 30.0m away is heard to hit the bell after 2.50 seconds. If the speed is 300.0m/s, what is the speed of the rock?

Question

Please show me how to solve using v_av=d/t.

Answer 1

I assume you also meant to say that the speed OF SOUND is 300 m/s.

 

There are 2 times here:

 

t₁ = time for the rock to reach the bell

t₂ = time for the sound of the rock hitting the bell to reach the thrower

t = t₁ + t₂ = 2.50 s

d = distance between thrower and bell = 30.0 m

u = speed of sound = 300.0 m/s

v = speed of rock toward bell = ?

 

t = t₁ + t₂

 

t = d/v + d/u = d(1/v + 1/u)

 

t/d = 1/v + 1/u

 

1/v = t/d - 1/u

 

v = (t/d - 1/u)^-1 = (2.50/30.0 - 1/300.0)^-1 m/s = 12.5 m/s