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Dumb Question ? Vf higher than D?

  1. Sep 13, 2013 #1
    Sorry if this is a dumb question but can the final velocity be higher than displacement/change in position?

    For example, if a rock is thrown in the water with the acceleration of gravity on a 15.3m high cliff, can final velocity be equal to 17.32m/s or is that incorrect?
     
  2. jcsd
  3. Sep 13, 2013 #2
    Of course it can! I'll quickly verify your answer.

    s=ut+1/2at^2
    0=-4.9t^2+15.3
    t = 1.77

    v=u+at
    = 0-9.8x1.77
    = -17.35m/s
     
  4. Sep 15, 2013 #3
    For your information, you cannot directly compare values with different units. The velocity is in meters per second and the height is in meters, so it doesn't make sense to say one is larger than the other. For example, 17.32 m/s is 0.02887 m/minute. It's the same velocity, but now the number is smaller than the number in the height.
     
  5. Sep 15, 2013 #4

    meBigGuy

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    Gold Member

    since the acceleration of gravity is 9.8m/sec/sec, you can calculate the distance at which the vertical freefall distance in meters equals the velocity in meters/sec. It is meaningless though.
     
  6. Sep 15, 2013 #5

    AlephZero

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    Science Advisor
    Homework Helper

    I think the OP is asking about the final velocity and the average velocity (total distance/total time).

    Of course the final velocity can be bigger than the average. The average of any set of numbers is always somewhere in between the biggest and smallest numbers, unless all the numbers are the same (which would mean the velocity was constant).
     
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