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Homework Help: Projectile motion

  1. Jun 9, 2007 #1
    1. The problem statement, all variables and given/known data

    If you have an object, say, falling off a cliff
    and you have initial velocity (Vox) can you assume that its Vf would be zero in both x and y if it doesnt state or ask for a final velocity before impact?
    eg) a car drives off a cliff and the site of impact is 32 m from the cliff, find Vo...can I assume Vf is 0?


    2. Relevant equations

    3. The attempt at a solution
  2. jcsd
  3. Jun 9, 2007 #2
    I do not understand why this assumption would be necessary.

    In the example of a car driving off a cliff, the solution can be found by finding the time it takes an object to fall the vertical distance of the cliff and then dividing the horizontal distance by that time. The final velocity does not come into play at all.

    Last edited: Jun 10, 2007
  4. Jun 10, 2007 #3

    Doc Al

    User Avatar

    Staff: Mentor

    Why in the world would you assume that? Falling bodies accelerate. The final speed of a body falling off a cliff will always be greater than its initial speed--not zero!

    What you can assume is that the horizontal speed of the falling body remains constant.
  5. Jun 10, 2007 #4
    if the final velocity is zero (which is just before the impact),
    then there would be no impact!!!

    do you mean something else by "vf" ??
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