Page 25 - Primary Seven Notes

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Types of friction

1. Static friction

It is found in objects which are fixed in one position. Static fric-

tion acts on objects when they are resting on a surface. For ex-

ample, if you are hiking in the woods, there is static friction be-

tween your shoes and the trail each time you put down your

foot. Without this static friction, your feet would slip out from

under you, making it difficult to walk. In fact, that’s exactly

what happens if you try to walk on ice. That’s because ice is
very slippery and offers very little friction.
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2. Sliding or Rolling friction

It is found in moving objects. Sliding friction is weaker than

static friction. That’s why it’s easier to slide a piece of furniture

over the floor after you start it moving than it is to get it mov-
ing in the first place. Sliding friction can be useful. For exam-

ple, you use sliding friction when you write with a pencil. The

pencil “lead” slides easily over the paper, but there’s just

enough friction between the pencil and paper to leave a mark.