Cross Section

A cross section is the 2D shape exposed when you make a straight slice through a 3D object

Imagine taking a straight knife and cutting directly through a solid shape

The flat surface that is revealed along the cut is called the cross section

If you slice a shape parallel to its base and get the exact same 2D shape every time, the cross section is uniform

Prisms are specific 3D shapes that have a uniform cross section along their entire length

Because of this property, a prism is always named after the 2D shape of its cross section (e.g., a triangular prism)

Slicing a solid cylinder horizontally, parallel to its base, creates a uniform cross section

This is the same 2D shape regardless of where you cut along the height

The horizontal cross section of a cylinder is always a circle

A vertical cross section is created by slicing a 3D object straight down, perpendicular to its base

When you slice a cylinder vertically through its center, you are cutting through its height and its diameter

This reveals a flat, 2D surface in the shape of a rectangle

The dimensions of this rectangle are equal to the height and the diameter of the original cylinder