- For a given volume, the sphere is the shape that has the smallest surface area. This why it appears in nature so much, such as water drops, bubbles and planets.
- The surface area of a sphere is exactly four times the area of a circle with the same radius. Why? because the area of a circle is πr2 and the surface area of a sphere is 4πr2
- Archimedes first calculated the volume and surface area of a sphere but first he had to figure out how to calculate the area of a circle.
- The ratio of a volume of a sphere inside a cylinder is 2:3
- The earth is not quite a perfect sphere so it's called a spheroid
- Start with a string and measure circumference of the sphere. The radius of a circle is equal to the circumference divided by 2π. Once you have radius, you can calculate the volume of the sphere.
- Submerge the sphere in a container of water and measure the displacement of water and then calculate the volume based on the amount of water displaced
Volume of a Sphere More free lessons at http://www.khanacademy.org
He uses a calculator in this video.
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