Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here


Parabola equation

Parabola equation

Parabola equation

Hi All,

I'm trying to figure out how to plot a parabola when I know the width and height of the parabola - I'm familiar with the standard parabola equation:


but I'm unclear as to what the variables other than x and y mean.

Any help would be appreciated.


RE: Parabola equation

i guess what you're saying is that you know two points on the parabola (since there is no end to a parabola (as a math function) and therefore no height or width).  using your terminology is guess the points you have are (-b/2, h) and (b/2,h)

i guess that you also know where the turning point is (0,0).

with three point you can substitute into the general parabola equation and solve the three equations for a, b, and c.  there are probably short-cuts, but pain is good.

RE: Parabola equation

Hi rb1957,

I use this for spinners on airplane propellers.  I realize there's probably a million ways spinners are designed, but right now (for the last several years anyway), I'm into parabolas for them - so essentially I know the base diameter - the max width for my purposes, and the length of the spinner - the max height for my purposes.  So these are the points I know, does that make sense?

RE: Parabola equation

yeah, you know the width and the height ...

so you know three points (0,0), (-w/2,h), (w/2,h).

substitute for (x,y) and get three equations in a, b, and c.

solve ...

btw, c = 0

RE: Parabola equation

Got it - Thanks rb1957!

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Close Box

Join Eng-Tips® Today!

Join your peers on the Internet's largest technical engineering professional community.
It's easy to join and it's free.

Here's Why Members Love Eng-Tips Forums:

Register now while it's still free!

Already a member? Close this window and log in.

Join Us             Close