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Homework Help: Need help - projectile motion with air resistance

  1. Oct 5, 2005 #1
    Need urgent help -- projectile motion with air resistance

    Consider a projectile fired vertically in a constant gravitational field. For the same inital velocities, compare the times required for the projectile to reach its maximum height (a) for zero resisting force and (b) for a resisting force proportional to the instantaneous velocity of the projectile.

    For a, I get t=-v0/a.
    For b, I have the equation F= m dv/dt=kmv-mg, which leads me to
    dv/dt=kv-g.
    Is this correct...If so, I can take it from here.
    If not what should it be?? What should my initial condition be to solve for the constant? Should it be v(t=0)=v0???

    Thanks much!!!
     
  2. jcsd
  3. Oct 5, 2005 #2

    Fermat

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    Homework Helper

    The resisting force is simply kv, rather than mkv and it is acting in the same direction as the gravitational force, mg.

    Initial/end conditions are vi = vo and vf = 0.
     
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