1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Homework Help: HINT Parabola

  1. May 21, 2008 #1
    HINT!!! Parabola

    An arch is in the shape of a parabola with a vertical axis. The arch is 15 ft high at the center and the 40 ft wide at the base. At which height above the base is the width 20 ft?

    [tex]V(0,15)[/tex] so my equation becomes: [tex](x-0)^2=-4p(y-15)\rightarrow x^2=-4p(y-15)[/tex]

    [tex]F(0,15-p)[/tex] & [tex]D:y=15+p[/tex]

    I can substitute 20 into my equation, but I don't know how to find p.

    Just a hint please :)
  2. jcsd
  3. May 21, 2008 #2
    Oh crap, I'm misreading the problem.

    Base = 40 ft. So at the axis of symmetry, it's 20 ft to the left & right. So that means the x value we're at for a total of 20 ft is actually x = 10?

    My point is P(10,y) ???
  4. May 21, 2008 #3


    User Avatar
    Science Advisor
    Homework Helper

    Oh rocomath!

    Forget all this detail. :frown:

    Hint: for a standard parabola through the origin, y is proportional to what? :smile:
  5. May 21, 2008 #4
    OH!!! hehe, I had my x-intercepts but yet I wasn't using them. Thanks for your time tiny-tim ;)
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook