Page 148 - Math Genius C2

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SurFacE oF objEctS

We identify whether a solid can stack, roll or slide,

by looking at its faces or surfaces. That means
stacking, rolling or sliding depends upon the nature

of the object’s surfaces.
Let us try to make a stack of cubical blocks as well

as balls.

Blocks can be stacked easily but we cannot put a ball on another
ball without external support. This is because a cube has a plane
surface and a ball has a curved surface.

If a solid is made up of only plane faces, it slides.
Here, we can see that the pencil box has plane faces. So, the box

is sliding.

If a solid is made up of only curved faces or surfaces, it rolls.

Here, we can see that the ball has only a curved surface.

So, the ball is rolling.

Some solids are made up
of both plane and curved

faces. Such objects can
roll as well as slide.

Here, we can see that the juice can has both
plane and curved surfaces. So, it is rolling and sliding.

Practice time 8d

1. Look at the given objects. Write which can roll, slide or stack.

Object

roll

Slide

Stack

146 Mathematics-2