**What is Sphere?**

You must have played or seen students playing football, basketball or table tennis. Football, basketball, table tennis ball are all examples of geometrical figures which we call “spheres” in three-dimensional geometry. If we consider the rotation of a semi-circle OAPB about its diameter AB, the rotation generates a sphere whose center is the center of the semi-circle and whose radius is equal to the radius of the semi-circle.

Thus, a sphere is the locus of a point in space which moves in such a way that its distance from a fixed point, in space, always remains constant. The fixed distance is called the radius of the sphere and the fixed point is called the center of the sphere. The difference between a sphere and a circle is that a sphere is a figure in three-dimensional space while a circle is a figure in two dimensions (in a plane) the longest straight line connecting two points passing through the center and its length is thus twice the radius is called the diameter of the sphere.

You can easily find the volume of the sphere and equation of sphere if you have the measurements of the radius and put it into a formula.

**Volume of a sphere= 4/3 πr ^{3}**

Example: What is the volume of a sphere with radius 3 feet?

Solution : Volume= 4/3 πr^{3}

= 4/3 x 3.14 x 33

= 4/3 x 3.14 x 3 x 3 x 3

= 113.04 feet cube

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