Introduction

In our daily life we may see objects like tennis ball, football, oranges,sweetlime etc. These are spherical in shape.

Sphere The set of all points in space which are equidistant from a fixed point is called a sphere. The fixed point is called the centre of the sphere and the constant distance is called its radius.

The segment through the centre of sphere, and with its end points on the sphere is called a diameter of the sphere.

A sphere can also be considered as a solid obtained on rotating a circle about its diameter.

If r is radius of sphere ,then

Surface Area of a sphere 4 r² sq. units

Volume of sphere 4/3r³ cubic units

Hemisphere A plane through the centreof a sphere divides the sphere into two equal parts, each of which is called a hemisphere.

If r is radius of hemisphere ,then

Curved Surface Area of a hemisphere 2 r² sq. units

Total Surface Area of a hemisphere 3 r² sq. units

Volume of hemisphere 2/3r³ cubic units

 

 

Spherical Shell The difference of two concentric spheres is called a spherical shell.

If R and r are outer and inner radii of a hemispherical shell , then

Surface area of shell = 4(R²- r²)

Volume of shell = 4/3(R³- r³)