sphere is a ball-shaped object. A hemisphere is half of a sphere.

e.g.Y9_Spheres_01.gifNumbersphere.jpg

There is one key measurement for a sphere, that is the radius, r.

Volume and Surface Area of a Sphere

The volume and surface area of a sphere are found using two formulae.

Y9_Spheres_02.gif

Volume

V = 43 π r3

 

Surface Area

S = 4 π r2

 

 

 

Examples of Sphere Calculations

Examples
Calculation

Find the volume of the sphere below.

Y9_Spheres_04.gif

Use π = 3.1

The radius of the sphere is 5 cm.

V = 43 π r3

V = 43 × 3.1 × 53

V = 516.7 cm3    (to 4 sig. fig.)

 

For the sphere shown above, find the surface area.

Use π = 3.1

Surface area =  r2

Surface area = 4 × 3.1 × 52

Surface area = 310 cm2

A sphere has a volume of 900 cm3, what is its radius?

Y9_Spheres_06.gif