“FRICTION IS A FORCE THAT ALWAYS PUSHES AGAINST AN OBJECT WHEN IT TOUCHES ANOTHER OBJECT” “WHEN 2 THINGS ARE IN CONTACT WITH EACH OTHER, THERE WILL BE FRICTION ACTING BETWEEN THEM”

What factors affect friction? Types of surfaces How hard the surface is How soft the surface is Texture of the surface How much Force is applied i.e. Gravity

High friction (lots of friction) – will slow something down and create a lot of heat Low friction (not much friction) – will keep things moving and reduce the creation of heat

Skis on the snow Car tire Brakes on a bike Water on a slide Pencil and eraser

Types of Surfaces Smoother the surface- smaller the friction  Ice  Glass  Tile The rougher the surface- greater the friction  Carpet  Roads  Sandpaper

How does adding rubber to the bottom of an object change the friction? What happens when the gym floor is dusty? How are other ways a surface changes the friction?

Types of Friction Static  Objects that aren’t moving  Think about trying to push something that just won’t move  Example: Push the wall. Sliding  Two solid surfaces slide over each other  Direction of motion is OPPOSITE that of friction  Example: Push your chair.

Types… cont’d Rolling  When an object rolls across a surface  Easier to overcome than sliding friction  Example: Push Mr. Bryan’s Chair. Drag  When a solid object moves through the Air  Easier to overcome than rolling  Example: Throw a Paper Airplane.

Paper Airplane Competition Aim: The winning team is the one who gets their plane to stay in the air the longest and is the fastest. Materials: 1 sheet of blank paper 1 paperclip Scotch tape Instructions: Use only the materials indicated in the above list; you don’t have to use them all. The plane may be constructed using all or part of the sheet of paper. Label each plane with your team name. Each group is allowed three throws; record the best throw only. Begin timing with the throw of the plane and end when the plane hits the floor. Settle a tie with a throw-off.