Surface Area of Sphere = 4 ∏ r2
You will need an orange, a knife, sticky tape and a ruler. Cut the orange in half and lay it with the flat side down. Tape the sticky tape from the top of the orange and go around and around the orange until it is covered with one layer of tape. Don't overlap. Now undo the tape and measure its length and its width. Calculate the area of the tape you used.
Now measure the diameter of the orange. Use the rule for SA of Sphere to work out the surface area of the orange. Compare your two calculations.
What is the area of plastic of a basketball with a diameter of 24 cm?
(Use ∏ = 3.14. Take care to use the radius.)
SA of sphere
= 4 ∏ r2
= 4 × 3.14 × 12 × 12
= 1808.64 cm2
In the Missouri Botanic Gardens in USA is a geodesic dome (almost a hemisphere). Its diameter is 53 metres. What is the approximate area of perspex (acrylic)? (Use ∏ = 3.14.)
SA of hemisphere
= (4 ∏ r2) / 2
= (4 × 3.14 × 26.5 × 26.5) / 2
= 4410.13 m2
Mix 5% detergent, nearly 50% glycerine (from the pharmacy) and nearly 50% water. Dip a wire loop in the mixture and blow!
There are many objects containing gas and liquid that have an efficient spherical shape. Consider the shapes of body cells and bubbles.
Design and carry out an activity that shows that:
This is a Nano-dragster using Bucky Balls for wheels. Nanotechnology has many functions from nano[ro]bots which can clear blocked blood vessels and delivering medication to targeted body cells, to super-conductors.