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Homework Help: Rectinilear motion

  1. Jun 16, 2008 #1
    Sara launches a model rocket in an open field near her house. Its trajectory is described by the function y=60ln(x+1)-6x for x=[0,36.15] where y is the rocket's height (in feet) above the ground and x is the horizontal distance (in feet) between the launch site and a point directly below the rocket.

    Given that the rocket's horizontal velocity (dx/dt) is 50 ft/s when it's directly over a point 20 (horizontal) feet from the launch site, determine the rocket's vertical veloctiy (dy/dt) at that point.

    I don't know how to go about solving this question, because normally the position is given as a function of time. Can someone help me? Thanks.
  2. jcsd
  3. Jun 16, 2008 #2
    Chain rule!

    dy/dt = ?
    find this and do value substitutions
  4. Jun 16, 2008 #3
    oh yeah!! i was overthinking it way too much. thanks though!
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