Circle
The object described is a cone. A cone has one vertex (the point where the flat face meets the curved surface) and one flat face (the circular base). Due to its shape, a cone can roll along a flat surface smoothly.
A cardioid is one possibility. See link, below.
In geometry, the only shape that has one surface is a plane.
A flat one! (:
A cone.
yes it has a flat bottom surface and one vertice
one
Well it has one edge, one face, one base(the face that the shape sits on), and one vertice.
a cone.
A cone.
The cone has only one vertice. It is the only three dimensional shape that has this characteristic. All others have more than one vertice.
none!all shapes are flat
half a sphere
There can be no such shape. If there were a shape with n flat surfaces, then if you sliced off one vertex, you would have a shape with n+1 flat surfaces. So it is always possible to add one more flat surface.
A cone.
A Cylinder
A square is a 2 dimensional shape with one flat surface area whereas a cube is a 3 dimensional shape with six flat surface areas.