What do you know about friction?

 Follow along as we review the answers to the friction questions.  ANSWER THE QUESTIONS ON THE PAPER THAT WAS PASSED OUT TO YOU.

 Write the type of KINETIC FRICTION SHOWN BELOW.

 Friction is a force between any two surfaces, that opposes motion.

a) The water is a lubricant that when spilled, fills in the hills and valleys on the floor and reduces friction between your feet and the floor

 Friction occurs because surfaces are covered with microscopic “hills and valleys” that stick to each other when they come in contact.

 Rough Surfaces have more hills and valleys that increase the force of friction. Smooth surfaces have less hills and valleys, therefore less friction occurs.

These surfaces will have more friction because they have larger hills and valleys than the other picture. This means they are more rough.

 If the force pushing the two surfaces together is great, the hills and valleys are in closer contact and friction is large. If the force pushing the two surfaces together is small, the hills and valleys are farther apart and friction is small.

More Force = More Friction

 Make a surface rougher  Push surfaces together harder

 Kinetic- sliding a book across the tabletop  Static- pushing a piece of furniture and it not moving.

 Sliding Kinetic Friction- moving a book across a desk, applying brakes in a car, scratching your arm  Rolling Kinetic Friction- wheels of a bike, toy car, trains on a track  Fluid Kinetic Friction- oil lubricating parts on a plane, car, or bike, water flowing through a hose

Apply what you know! You and a friend are trying to move this piano across carpet and are struggling to make it move. Why is it so difficult to move the piano? What can be done to make the piano move easily across the floor?