As the disk slips, there is a friction force acting to the left on the disk at the contact point. During slipping, the friction force opposes the direction of motion of the contact point – that is, ...

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 ...