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Homework Help: Finding g,time,&height with magnitude of velocity

  1. Sep 21, 2009 #1
    Your spaceship lands on an unknown planet. To determine the local value of g , you ask a steel-toed crew member to kick a stone, and you find that if she kicks it at 18.0 m/s at various angles, the maximum range she can achieve is 34.8 m .
    What is g (m/s)? time (s)? and height (m)?

    I decided to use the knowledge of velocity given. Vox= Vocos[tex]\theta[/tex]
    I also knew that at 45° maximum distance may be achieved. However, I never did a problem with these unknowns in my physics class so I feel lost as to how to solve it. Any suggestions?
  2. jcsd
  3. Sep 21, 2009 #2
    I have worked through some problem solving methods that I think I need to go through to get to the next steps. I know that I need to solve for acceleration but I'm unsure as to how to do that with the equation y= yo+voyt+1/2at². Once I get the acceleration I believe I can just divide that figure by 9.8m/s² to get the value of g on the planet. Any suggestions are more than appreciated.

    Thanks a ton!
  4. Sep 22, 2009 #3


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    Hi Kyle! :smile:
    uhh? :confused:

    the acceleration is the value of g on the planet. :wink:

    Find it (using 45º) by finding t for which y = 0, then find the a for which x = 34.8 at that value of t. :smile:
  5. Sep 22, 2009 #4
    g= Vo^2sin(2a)/R ? Does that make sense for an equation finding g?
  6. Sep 23, 2009 #5


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    Do you mean g = v02sin2θ/R? How did you get that?

    (btw, remember sin45º = 1/√2)
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