Surface area of spheres- an apeeling lesson…

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6 Responses

  1. Dani Quinn says:

    I love this! Any thoughts on volume of spheres?

    • Don Cohen says:

      Volume Relationship Set – Ideal School Supply Co., Alsip, IL 60482

      The set contains other shapes, but we use the cylinder and the sphere. We assume the volume of the cylinder is = Pi*r^2*h. The sphere has the radius = to the radius of the cylinder, and the height of the cylinder = 2*r of the sphere. You fill the cylinder with water that’s in a bucket. Then stuff the sphere into the cylinder. Using Achemedes’ law, the amount of water displaced = the volume of the sphere. You look at the volume of water left in the cylinder and guess about 1/3 full. That means the vol. of the sphere is 2/3 the Vol of the cylinder.. So the vol.of the Sphere = (2/3)*Pi*R^2*2*r = (4/3)*Pi*r^3 which is correct.

      One can find the Vol of a cone compared to the vol of a cylinder, and a pyramid compared to a cube. The pieces are sturdy and have lasted for quite a while.

  2. Looks like an excellent lesson. šŸ™‚

  3. Marshall says:

    Not sure about the lesson but that joke is pure gold!

    OK, the lesson is pretty good too.

  4. Lloyd Knox says:

    Just found your post after we did a similar exercise at home that was also kind of opposite. Opposite because we tried to cover a curved thing with flat things. Instead of oranges and a sheet of paper we used pancakes and a basketball:

  1. 02/12/2016

    […] about the surface area of a sphere using an orange that you unpeel. It’s described on this wonderful blog by William Emeny. (His blog’s name is eerily similar to my […]