# Homework Help: Ignore the speed of sound?

1. Apr 3, 2009

### katyross

1. The problem statement, all variables and given/known data
"A rock thrown horizontally at a large bell 50m away is heard to hit the bell 4.5 seconds later. If the speed of sound is 330m/s, what was the speed of the rock? (Disregard the effect of gravity.) [Hint: If it requires a time of t for the sound to return, then it requires (4.5 s-t) for the stone to reach the bell]

2. Relevant equations

v = d/t

3. The attempt at a solution

Would you completely disregard the speed of sound, and continue using the v= d/t?

v = 50 / 4.5
v = 11.1 m/s

2. Apr 3, 2009

### cristo

Staff Emeritus
No, I would use the speed of sound, and the hint.

3. Apr 3, 2009

### katyross

how would you fit that into the forumla to find the speed of the rock?

4. Apr 3, 2009

### cristo

Staff Emeritus
It tells you that if t is the time the sound takes to travel from the bell to your ear, then (4.5-t) is the amount of time the stone takes to travel to the bell.

How can you calculate t, given the speed of sound and the distance travelled?

5. Apr 3, 2009

### katyross

v = d/t

t= d/v
(4.5-t) = 50/330

?

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