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Urgent Plz Help

  1. Sep 30, 2007 #1
    [B][/B] A runner accelerates to a velocity of 4.15 m/s due west in 1.5 s.His average acceleration is 0.640 m/s also directed to the west . Wat was his velocity when he began accelerating ?
  2. jcsd
  3. Sep 30, 2007 #2
    You can use the equation:

    [tex]V_{final} = U_{initial} + at[/tex]

    V = Final Speed
    U = Initial Speed
    a = Acceleration (use your average acceleration)
    t = Time across which the acceleration is applied

    I will help you rearrange the equation if you need, but as the sticky suggests, this forum isnt here to give you homework answers, and most of the official PF helpers here will use an analogous equation to help guide you.

    EDIT: Whoops got the equation a bit messed up there.
    Last edited: Sep 30, 2007
  4. Sep 30, 2007 #3
    yea but how ..... thanks for ur help???
  5. Sep 30, 2007 #4
    Well acceleration speeds things up, reguardless of their initial velocity, in the equation, U is the initial velocity, and "at" is the amount the original velocity has increased by to get to the final velocity, acceleration multiplied by time equals the velocity increase, so the equation technically is

    [tex] V_{final} = U_{initial} + X_{increase} [/tex]​

    Where "X" is the amount the initial speed has increased by to reach the final speed.
    Last edited: Sep 30, 2007
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