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Homework Help: Falling rock

  1. Sep 14, 2004 #1
    rock is dropped from cliff. it is heard hitting the ocean 3.00s later, if speed of sound is 340m/s, how high is the cliff?

    im so stuck
  2. jcsd
  3. Sep 15, 2004 #2


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    Gold Member

    try d= (at^2)/2
    a = acceleration
    t = time
    d = distance
    use the speed of sound in dry air at sea level to solve.
  4. Sep 15, 2004 #3
    Hi -

    This is how I would approach this problem...

    Draw a sketch to represent the situation. As you can see, the rock is in free fall from y (the height of the clift to the ground) to the ground (y = 0). The soundt travels with uniform speed the distance y (upward). Let t1 be the time of the free fall and t2 the time of the sound traveling up. Then, the total time is t = t1 + t2 = ?. Then, use the free fall formula to get time t1 and then solve for the height of the clift.

    Good luck :smile:
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