Do a selection of the activities. See notes for different lesson plans I have done.
Optional coin game in its simple form with just flicking a coin across different surfaces is good to start with for students to discover and define friction.
Define and demonstrate friction:
Friction is a force that slows things down. It happens when two things rub together.
If I slide this block, it stops after a while, because the block is rubbing against the cardboard.
Students slide blocks down ramps at their desks.
Discuss the surfaces and talk about why they have the least and most friction.
Bumpy surfaces rub against the block more, and slow it down more.
Write on board: under less friction put smoother surface, under more friction put bumpier surface.
Show how friction can be reduced
A fun challenge to reinforce how to reduce friction: Reduce friction to move the teacher.
Friction on a bike to show friction and reduced friction used to our advantage.
Wrap up discussion, ending with:
Why do our hands get warm when we rub them?
Friction! Friction makes heat.
Man first made fire by rubbing two sticks together (500,000 years ago) - the friction between them makes so much heat that it can start a fire.