Friction

Warm up• Come in quietly, get your journal from the

appropriate bin, complete the following on the next available page:

• Draw the force diagram of Susie pushing her bike to the left with 400 N of force, and Roger pushing his bike to the right with 800 N of force. (Remember arrow size and direction)

• Draw the force diagram of a falling bowling ball weighing 20 N (Remember gravity is a force).

Two Masses Falling

Steel Ball and a Feather

Standards

• S8P3b. Demonstrate the effect of balanced and unbalanced forces on an object in terms of gravity, inertia, and friction.

Daily Goals

• Explain how friction works• Give examples of the two types of friction• Explain how friction can be helpful and

harmful

Essential Question

• How does friction help football players?

Important

• Test Friday, Nov. 18• Practice Sheet #12 due Friday, Nov. 18• Study Guide due Friday, Nov. 18 for extra

credit

Friction

• Friction - a force that opposes motion between two surfaces that are in contact

Direction of Friction

• Friction always works in the direction opposing motion

Friction

Types of Friction

• Two main types of friction– Static friction – occurs when a force is applied to

an object but does not cause motion– Kinetic friction – Friction between moving surfaces

Warm Up

• Come in quietly, get your journals, and have a seat.

• Open your journals and complete the writing prompt “A World without Friction”

• You have ten minutes to be finished. (Not just starting, but completely finished. Finished means several complete sentences addressing the prompt). For a grade.

Kinetic Friction

• Three types– Rolling– Sliding– Fluid

Types of Friction

How to Increase/Decrease Friction

• Greater forces applied to the object increase friction

How to Increase/Decrease Friction

• Rougher surfaces on the objects increases friction

VS.

How to Increase/Decrease Friction

• The amount of area in contact does not affect friction

How to Increase/Decrease Friction

Friction - Helpful

Friction - Harmful