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Homework Help: Position Time, falling objects

  1. Jun 25, 2010 #1
    Please help! Ive been both conceptually blocked for quite some time and need help fast!
    A rock is dropped from a sea cliff, and the sound of it striking the ocean is heard 4.0 later. Given the speed of sound is 340m/s, calculate how high the cliff is in meters.
  2. jcsd
  3. Jun 25, 2010 #2


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    If h is the height of the cliff, time taken by the rock to fall is given by

    h = 1/2*g*t1^2.

    Time taken by the sound to reach the top of the cliff is t2 = h/340.

    Now t1 + t2 = 4 s.

    Substitute the values of t1 and t2 in the above equations and solve for h.
  4. Jun 25, 2010 #3

    So do you mean solve to T1 in the first equation, then add the two together and solve for h?
  5. Jun 25, 2010 #4
    Get t1 in terms of h. Then get t2 in terms of h.
    & Substitute these into t1 + t2 = 4.
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