Friction 1
• Introduction

Why is it difficult to drag a heavy object along the ground, but so much easier if it is on wheels? Why is it easy to slide things along some surfaces but not others? The answer is a force called friction

When two things rub together it causes friction. Friction slows things down and stops them moving. The amount of friction there will be is determined by how much contact there is between the surfaces of the moving objects and by how rough or smooth the surfaces are.

A wheel or a ball roll freely over a surface because only a small part of it is in contact at any one time. An icy surface is slippery because it is so smooth.

Try out this worksheet to test what you know about friction.

• Question 1

You are sitting on the side of a grassy hill enjoying the view. What stops you from sliding to the bottom?

holding on

air pressure

gravity

friction

• Question 2

Why would it be a harder for the dogs to pull the sled on a stony surface?

their paws would get caught between the stones

the stones would be too warm for the sled

the rough stones cause more friction with the sled runners

• Question 3

True or false: friction only happens when moving objects come into contact with each other.

true

false

• Question 4

Why does putting grit on icy roads in winter help to stop cars from skidding?

the grit makes the road surface sticky

the grit makes the cars go more slowly

the grit makes the road surface less smooth and increases friction

• Question 5

Why do skiers put wax on their skis?

it makes them easier to see

it helps the skis grip the snow

it lets them go faster

• Question 6

Which of these is an example of friction being useful?

the brakes on a bicycle

a rusty door hinge

• Question 7