Page 78 - Mathematics Class - IX

ACTIVITY 5.3

OBJECTIVE

To obtain the formula for the surface area of a sphere.

MATERIALS REQUIRED
Cardboard/wooden strips String A spherical ball

Thick sheet of paper Measuring tape Scissors/cutter
Ruler Adhesive Pin

PRE-REQUISITE KNOWLEDGE
1. Basic knowledge about shape of a sphere. 2. Basic concept of a circle and its area.

THEORY
A sphere is a three-dimensional figure which is made up of all points in the space, lies at a constant distance, from
a fixed point called the centre of the sphere and the constant distance is called its radius.

The shape of a sphere is round and it does not have any faces, any vertex, any edge.
Basically, it is perfectly symmetrical.

PROCEDURE
1. Take a spherical ball and find its diameter (d) by placing it between two vertical boards (Fig. (a)).

d
Fig. (a)

2. Mark the topmost part of the ball and fix a pin (Fig. (b)).

Fig. (b)

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