1.1 What is friction? Take this everyday example: when a coffee mug rests on a flat table, the kinetic frictional force is zero. There is no force trying to move the mug across the table, so there is ...

When friction acts between two surfaces that are moving over each other, some kinetic energy is transformed into heat energy. Friction can sometimes be useful. For example, we rely on the soles of ...

Ice causes very little friction, which is why it is easy to slip over on an icy day. However, this is a good thing for ice skating and sledging. Friction is a force between two surfaces that are ...