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Homework Help: Finding instantaneous velocity of objects in projectile motion

  1. Mar 16, 2008 #1
    1. The problem statement, all variables and given/known data
    No air resitance
    Initial speed 8 m/s
    inst. time at 3 s

    Find instantaneous velocity at 3s.

    Components of displacement:
    dx= 24
    dy= 44

    2. Relevant equations

    d=v1t+(1/2)a(t)^2 or other kinematics equations

    3. The attempt at a solution

    I tried to find the components of the velocity using the components of the displacement (d/t=v). But both my answer and angle of direction were wrong. How do i do this?
  2. jcsd
  3. Mar 16, 2008 #2


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    Homework Helper

    So dx and dy are those values at t=3?
    If so consider Vertical motion:

    where u is the initial vertical velocity. Sub t=3 in there and get u. and well you know how to get the horizontal component (v=d/t as you stated before)
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