Page 75 - Mathematics Class - IX

ACTIVITY 5.2

OBJECTIVE

To find a formula for the curved surface area of a right-circular cylinder, experimentally.

MATERIALS REQUIRED

Coloured chart paper
Adhesive tape
Ruler
Pencil
Scissors

PRE-REQUISITE KNOWLEDGE

1. Concept of a rectangle and its area.
2. Concept of circle and terms related to it.

3. Concept of a cylinder.

THEORY

1. For concept of circle refer to Activity 4.6.
2. Right-circular cylinder: A solid generated by the revolution of a rectangle about one of its sides which is
kept fixed is called a right-circular cylinder. The fixed side of the rectangle about which it rotates, is called
the axis of the cylinder.

PROCEDURE

1. Take a rectangular coloured chart paper having length a units and breadth b units (Fig. (a)).
2. Now, folding the chart paper along its breadth, fix both ends by using adhesive tape and obtain a cylinder
(Fig. (b)).

a

b

Fig. (a) Fig. (b)

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