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Homework Help: Find the magnitude of the velocity vector on impact

  1. Nov 4, 2008 #1
    (resolved) find the magnitude of the velocity vector on impact

    Thelma and Louise drive their '66 T-Bird convertible off a cliff. They are going 25.9 m/s and the cliff is 97 meters high. Find the magnitude of their velocity vector the moment they impact the ground. Make sure you do the following in your answer:

    DO NOT include units. We'll deal with that in the next question.
    Give precision to tenths (#.#).
    Make your answer correct to within 0.2

    so given y is -97, and vi is 25.9 m/s


    equations for horizontal projectile motion for vf are
    vyf=-g(t)
    vf=sqrt of (vxf^2+vyf^2)
    so far for t i had 4.447seconds

    ____
    \/-2*-97
    ----------= 4.447
    9.81
    and had vyf as -44.6m/s
     
    Last edited: Nov 5, 2008
  2. jcsd
  3. Nov 4, 2008 #2

    mgb_phys

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    You don't need the time.
    You can use vf2 = vi2 + 2as for the vertical velocity
    Since you ignore air resistance there is no change in the horizontal velocity.
     
  4. Nov 4, 2008 #3
    And think of vxf and vyf as being two legs of a right triangle. The answer you're looking for is the hypotenuse of this triangle.
     
  5. Nov 4, 2008 #4
    what is 2as????
     
  6. Nov 4, 2008 #5

    mgb_phys

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    2 * acceleration * distance
    It's one of the standard motion equations - although some books use different letters.
     
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