Cutting Corners
This is a Level 3 Geometry activity from the Figure It Out Series.
A PDF of the student activity is included.
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identify three dimensional shapes.
rubber bands or string
FIO, Level 2-3, Geometry, Cutting Corner, page 24
model spheres, cylinders, and cones
“Solids of revolution” are created when a flat (two-dimensional) shape is rotated about an axis.
Activity One
As the circle turns, its rotational image is a sphere, like the shape of a basketball or a planet.
Activity Two
The rotational image of a rectangle is a cylinder.
Activity Three
The rotational image of the triangle is a cone.
Students may wish to investigate the rotational images of other shapes, such as:
Some examples of solids of revolution are woodturning on a lathe and figure skating.
Answers to Activities
Activity One
1. A sphere
2. The list could include balls, marbles, soaps, parts
of buildings, poi, and oranges.
Activity Two
1. A cylinder
2. The list could include paper rolls, tins, jars,
poles, and tubes.
Activity Three
1. A cone
2. The list could include ice-cream cones, traffic
cones, and turrets.