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What’s rubbing?
1 Copy these sentences and fill in the gaps.
Friction is a
caused by two
moving over each other.
surfaces produce more friction than
surfaces.
Friction can be helpful, because it stops us
when we walk, and
that slow down cars or bicycles could not work without friction.
Friction is not always useful. It can cause
and
away things that rub against each other.
, and
Oil can reduce the amount of
. Oil stops the surfaces touching each other.
.
Liquids that reduce friction are called
2 Look carefully at these pictures.
A
B
C
D
E
For each picture:
a Describe where there is friction.
b Say whether the friction is helpful or unhelpful.
c Describe how the friction could be increased or decreased.
For example:
A There is friction between the girl’s trousers and the grass. This is useful friction
because it stops her sliding down the hill. She could increase this friction by wearing
a rougher material.
S
knowledge
Exploring Science for QCA
Copymaster File 7
513
© Pearson Education Limited 2002
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