Friction can be both helpful and unhelpful. Helpful friction is used in brakes to slow bikes and in parachutes to slow skydivers during descent. However, unhelpful friction causes wear and tear over time, requiring the replacement of tires on racing cars and engine parts. While friction can be increased using special materials like rubber for rock climbing shoes and knots, some materials like PTFE aim to reduce friction for non-stick surfaces.

1. Helpful friction
People often use friction to slow things down.
These brake blocks use friction to slow
the bike wheels.
When the skydiver
opens the parachute,
air resistance slows
him down.
Air resistance is a form of friction.

2. Unhelpful friction
The main problem with friction is that it wears
things away so they need to be replaced.
The tyres on the racing car will
often need to be replaced as
friction wears them down.
Friction also wears engine parts,
so they need replacing.

3. Unhelpful friction

4. We can
increase
friction by
using certain
material
Rock climbing shoes are
made from special rubber
that increases friction
and gives a good grip
Friction keeps knots done
up and helps the climber
to control the rope

5. A Gecko’s foot

6. PTFE Very
low friction
Non stick
surfaces