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Chapter 1 Lesson 3. Friction. Objectives of the lesson. To explain why friction occurs. To list the two types of friction, and give examples of each type. To explain how friction can be both harmful and helpful. Friction.
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Chapter 1 Lesson 3 Friction
Objectives of the lesson • To explain why friction occurs. • To list the two types of friction, and give examples of each type. • To explain how friction can be both harmful and helpful.
Friction • Friction is a force that opposes motion between two surfaces that are in contact. • Source of Friction: • The rough surface of any object is rough and contains hills and valleys. • When they are in contact with other object’s hills and valleys, friction occurs. • Friction is affected by the following factors: • The force pushing the surfaces together. • The roughness of the surfaces.
The effect of Force on Friction • If the force pushing the surfaces together increases, the friction increases because surfaces become closer. • When the object weighs more, it exerts more force.
The effect of rougher surfaces on Friction • The rougher the surface is, the greater the friction is, because rough surfaces have more microscopic hills and valleys.
Types of friction: • Kinetic friction: is the friction between moving objects. • a) surfaces can slide past each other. • b) a surface can roll over another surface. • 2. Static friction: When a force balances the forces applied on an object causing it not to move.
Ways to reduce friction: • To use lubricants. • Examples are: motor oil • grease Ways to increase friction: • 1. Make surfaces rougher. • Example: wearing batting gloves. • 2. Increase force pushing the surfaces together • Example: sponge with a rough surface • scrubber