Parabola or an ellipse?

[don1231915]

Parabola or an ellipse??

Homework Statement

I have a curved structure which looks like this:
http://imageupload.org/pt-1412920046522.html

I haven't been told specifically what it is.
I assumed it to be ½ellipse. It has a height of 36m. So, I also found out the equation y= sqrt(1296-x^2).
Could this also be a parabola? If so, how would I find the equation when I only know the following things:
height - 36 m
It has a rectangular base 150m long and 72m wide.

I just want to know if I am right with the half ellipse?

PLEASE HELP

THANKS

Homework Equations

The Attempt at a Solution

 

[Mark44]

Homework Statement

I have a curved structure which looks like this:
http://imageupload.org/pt-1412920046522.html

I haven't been told specifically what it is.
I assumed it to be ½ellipse. It has a height of 36m. So, I also found out the equation y= sqrt(1296-x^2).
Could this also be a parabola? If so, how would I find the equation when I only know the following things:
height - 36 m
It has a rectangular base 150m long and 72m wide.

I just want to know if I am right with the half ellipse?

The equation you show represents the upper half of a circle of radius 36, centered at the origin. You can get this by squaring both sides of the equation you have, resulting in x² + y² = 1296, with y >= 0. This equation doesn't appear to match the image you uploaded, although if the image is stretched in the vertical direction, that would make the vertical cross section look like a half ellipse rather than a half circle.

The roof of the structure (as opposed to the vertical cross section) is a surface in three dimensions. The surface in the image might be an elliptic cylinder or a parabolic cylinder, two kinds of surfaces in 3-D space.