Prisms
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.
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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. |
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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 ! |
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No Curves!
A prism is a polyhedron, which means the cross section will be a polygon (a straight-edged figure) ... so all sides will be flat!
For example, a cylinder is not a prism, because it has curved sides. |
These are all Prisms:
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| Square Prism: |
Cross-Section: |
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| Cube: |
Cross-Section: |
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(yes, a cube is a prism, because it is a square
all along its length)
(Also see Rectangular Prisms
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| Triangular Prism: |
Cross-Section: |
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| Pentagonal Prism: |
Cross-Section: |
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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: |
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(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
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Volume = Area × Length
Example: What is the volume of a prism whose ends are 25 in2 and which is 12 in long:
Answer: Volume = 25 in2 × 12 in = 300 in3
(Note: we have an Area Calculation Tool) |
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