A prism has the same cross section all along its length !
A cross section is the shape you get when cutting straight across an object.
The cross section of this object is a triangle ...
.. it has the same cross section all along its length ...
... and so it's a triangular prism.
Try drawing a shape on a piece of paper (using straight lines!),
then imagine it extending up from the sheet of paper,
- that's a prism !
No Curves!
A prism is officially a polyhedron, which means all sides should be flat. No curved sides.
So the cross section will be a polygon (a straight-edged figure). For example, if the cross section was a circle then it would be a cylinder, not a prism.
These are all Prisms:
Square Prism:
Cross-Section:
Cube:
Cross-Section:
(yes, a cube is a prism, because it is a square
all along its length)
(Also see Rectangular Prisms
)
Triangular Prism:
Cross-Section:
Pentagonal Prism:
Cross-Section:
Regular and Irregular Prisms
All the previous examples are Regular Prisms, because the cross section is regular (in other words it is a shape with equal edge lengths)
Here is an example of an Irregular Prism:
Irregular Pentagonal Prism:
Cross-Section:
(It is "irregular" because the
Pentagon is not "regular"in shape)
Volume of a Prism
The Volume of a prism is simply the area of one end times the length of the prism
Volume = Area × Length
Example: What is the volume of a prism whose ends are 25 in2 and which is 12 in long:
HOME
