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Homework Help: Velocity of Sound, speed of rock and return of sound

  1. Feb 3, 2010 #1
    1. The problem statement, all variables and given/known data
    Rock is thrown vertically towards a bell 50m away, you hear the bell ring 4.5 seconds later, how fast was the rock travelling, assuming the speed of sound is 330m/s

    2. Relevant equations

    3. The attempt at a solution
    I like to draw my questions out, then fill in the data, so i'll do that first, if you don't wish to see it please scroll down a bit
    4.5 seconds for return of sound
    ^Starting position 50m
    Speed of sound 330m/s
    Distance 50m
    4.5 seconds for sound to return from throwing it

    Now, first I wanted to find how long it would take the sound to get back after it hit the bell so I looked for time
    T = D/V

    T=50m / 330mps

    I then tried to find the velocity it would take for the rock to reach the bell on it's own,
    so I looked for the time again, from which I could distract the time it took for the sound from

    V = D/T
    V = 50m / 4.5s
    V = The rock was going for 11.11111mps IF the sound was instantaneous, I've no idea how to subtract 0.15151515s from 11.11111mps

    I don't know if I missed something during instruction, but I've just started physics and this could be stupid, but I've no clue where to go from here.

    The answer for checking your answer is 11.5mps
  2. jcsd
  3. Feb 3, 2010 #2


    User Avatar
    Homework Helper

    hi Chrisss, welcome to PF.
    Time taken by the stone to strike the bell is ( 4.5 - 0.1515) s
    Now find the velocity of the stone.
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