It could be a semi-sphere but mostly it's a cone.
a cylinder
A circle
A cone. It has a circle for the base, and a curved face tapering to a point.
a circle
A plane circular face and a curved shape which, if flattened out would be a sector of a circle.A plane circular face and a curved shape which, if flattened out would be a sector of a circle.A plane circular face and a curved shape which, if flattened out would be a sector of a circle.A plane circular face and a curved shape which, if flattened out would be a sector of a circle.
Semi Circle
The answer is - a cone.
There cannot be such a shape. It is not a cylinder because a cylinder sdoes not have a rectangular face. A rectangle must be a flat face and the only flat faces in a cylinder are the circle faces. The curved face can be "opened out" into a rectangular shape but because the face is curved it cannot be rectangular.
a cone
Tricky question, because you said 'one face'. A face is usually associated with a three-dimensional object, and a side is usually associated with a two-dimensional object. However, I think I know what you're getting at: It could appear to be a sphere (three dimensional). It is a circle (two dimensional). Keep in mind, that spheres technically have an infinite number of faces (not one), but it's deceiving because you can't see the individual faces of a sphere as they are infinitesimally small and the mind wants to think of it as having only one face since a sphere looks exactly the same no matter what angle you're viewing it from. A circle has one face, of course -- but infinite _sides_. How does that answer your question?
A figure that has a curved face or curved edge.
a circle has no face a sphere on the other hand does