2 objects are a race track and an egg. I know this because it was part of my science homework.
Chat with our AI personalities
Spheres
There are an infinite number of possibilities. Let A metres be any positive length and let B be 10/A metres. Then the rectangle of size A*B will have an area = A*B = 10 sq metres. Furthermore, there is no requirement for the shape to be a rectangle. It could be a circle, ellipse, triangle etc or a completely irregular shape whose length and width are difficult to define.
20cm.
An inscribed polygon
Once again the answer from The WikiAnswers Community is wrong. The triangle is an obtuse angled isosceles triangle. And, as inanimate objects, triangles are not usually prone to become pregnant!