You will get a rectangular prisim
a circle
it depends in what shape the diamond is cut Another Answer As a raw stone, a diamond can be shaped like a pyramid, or two pyramids joined at the base. Can you count the corners in the two-pyramid example?
when you cut a pentagon in half you create a trapizoid
A trapezium, except that when it goes through the apex, it becomes a triangle. If the pyramid is a right pyramid, then the cross sections will be isosceles.
Depends where you make the cut Across the planes it is a CUBOID Across the corners it is PYRAMID .
It would be a wooden cube that has been cut in half and painted red.
Dome
If you cut a rectangle in half you wouldn't get a solid figure at all, since a rectangle is a plane figure. If you made a straight line cut you would get either a triangle or a quadrilateral of some variety depending on exactly how the cut was made.
Another cylinder
It is called a frustum.
A triangle
Trapizoid &triangle
A rectangular prism or a cuboid.
square
Not exactly. A frustum would be a pyramid with the apex cut off. A truncated pyramid would be a pyramid with all vertices cut off.
A hemisphere is half a sphere (half a ball, cut through the middle). A pyramid looks like an Egyptian 'Pyramid' (see the related link below).