Please have out: - SISN -Pencil - Glue - Scissors When you have ALL your materials on your table: With your seat partner brainstorm/write down all the ways motion can be changed or influenced.

Friction

Friction A force that opposes motion between two surfaces that are in contact.

Source of Friction All surfaces have hills and valleys. When two surfaces are in contact, the hills and valleys of one surface stick to the hills and valleys of another.

Amount of Friction Amount of friction depends on many factors. Two factors are the strength of the force pushing the surfaces together and the roughness of the surfaces.

Amount of friction More force exerted causes more friction. The rougher the surface, the greater the friction.

What will cause more friction?

Kinetic Friction The friction between moving surfaces. The amount of kinetic friction depends on how the surfaces move.

Examples of Kinetic Friction Sliding-Brakes on a bicycle Sliding-Writing Rolling-Wheels

Static Friction Static friction occurs when a force is applied to on object but does not cause the object to move.

Static vs. Kinetic Friction Static friction disappears as soon as an object starts moving and then kinetic friction immediately occurs.

Harmful VS Helpful Friction Harmful Examples Friction causing holes in pants, Wearing down engine parts Reduce by adding a lubricant like oil or ball bearings Helpful Examples Brakes on a car, Friction lets you walk without slipping Increase by adding roughness or adding force

Friction 500 Activity

On a separate sheet of paper…. You are an engineer hired by NASCAR to build a new racetrack in Greenville, NC. You need to determine what materials you will use and why you are using those materials. Explain why this year’s most prestigious race should be run on your racetrack. Use what you know about forces, motion, and friction to create your racetrack and write your explanation persuading the NASCAR community to come to our new track in Greenville!