All about friction

Friction is a force caused when one surface rubs against another. It can make things harder to move.

Let's find out more about friction and how it affects moving objects.

Watch this video to learn more about friction. Find out about different types of friction and how we can increase or reduce it.

When two surfaces rub against each other, they create friction.

For example, when you try to push a box along the floor, friction makes it difficult.

• Friction is a force that resists the movement of objects past each other.

• Friction always works in the opposite direction to the direction the object is moving.

• Friction always slows or stops a moving object. It can also prevent objects from moving.

The amount of friction depends on the materials from which the two surfaces are made. The rougher the surface, the more friction is produced.

Air resistance is one kind of friction.

Air resistance is a force that occurs between a moving object and the air that surrounds it.

Like all friction, it always slows the rate at which the object moves or falls.

Air resistance increases with surface area, so the more surface area, the more air resistance.

This is how parachutes allow people to safely jump out of planes. The large surface area of the parachute produces lots of air resistance. This slows down their fall.

Water resistance is another kind of friction.

Water resistance is a force that occurs between an object in the water and the water that surrounds it.

It always works to slow things down, too.

When you walk through water you can feel the force of the water resistance making it difficult for you to move.

Friction can be both a helpful and unhelpful force.

Helpful friction

• Friction between our shoes and the floor stop us from slipping.
• Friction between tyres and the road stop cars from skidding.
• Friction between brake blocks and a wheel lets a cyclist stop their bike.

Think of what happens when you rub your hands together quickly – they warm up. The friction force generated by rubbing your hands becomes heat energy.

Unhelpful friction

• If you are trying to swim quickly, then water resistance can slow you down.
• If a bike chain isn't lubricated, friction makes it more difficult to turn the pedals.
• If shoes rub against your feet the friction might cause a blister. Ouch!

In racing sports it is better to be as fast as possible to win. In these sports reducing the force of friction is important.

Less friction means more efficient movement as less energy is lost to friction forces.

In motor sports, the shape of the racing car is very important. They are designed to be as aerodynamic as possible.

This means that the shape of the car allows air to flow over the surface of the car more easily. This reduces air resistance and leads to less friction acting on the car. As a result, the car can move faster.

Aerodynamic – objects designed to reduce air resistance.

Air resistance – a form of friction caused by air.

Friction – a force that acts on moving objects.

Water resistance – a form of friction caused by water.

Try this friction experiment!

How does friction affect how fast a toy car can travel? Let's find out!

You will need:

• A toy car

• A ramp

• Some surfaces to test:

  • A smooth surface
  • A rough surface such as sandpaper
  • A soft surface such as a tea towel

Watch the video to find out more.

Think you've got to grips with friction? Find out in our fun quiz!