Friction: A Force That Opposes Motion

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1 Friction: A Force That Opposes Motion Station 3

2 Think About It: Climbing a vertical rock wall means pitting your strength and stamina against the force of gravity, which pulls you down toward the ground. Another force helps you to climb the vertical rock wall by keeping your hands and feet from slipping. That force is friction.

3 1. Definition Friction is a force that resists motion between two objects in contact.

4 2. Source of Friction When two surfaces are in contact, the microscopic hills and valleys of one surface stick to the tiny hills and valleys of the other surface. This contact causes friction.

5 Try it! Rub your hands together really fast!

6 3. Try it! Explain how rubbing your hands together is an example of friction. What is a product of friction?

7 4. Friction Opposes Motion: Friction always works in the direction opposite from the direction the object is moving, or trying to move. Friction always slows a moving object down.

8 5. More or Less Friction The amount of friction depends on the materials from which the two surfaces are made. The rougher the surface, the more friction is produced.

9 5. More or Less Friction Example: You would have to push a book harder to get it moving on a carpet than you would on a tile floor. because there is more friction between the carpet and the book than there is between the wood and the book.

10 Types of Friction Static Sliding Rolling

11 Static Static friction acts on objects when two surfaces are in contact.

12 Static Example: If you are hiking in the woods, there is static friction between your shoes and the trail each time you put down your foot.

13 Static Without this static friction, your feet would slip out from under you, making it difficult to walk. In fact, that s exactly what happens if you try to walk on ice. That s because ice is very slippery and offers very little friction.

14 Static Can you think of other examples of static friction?

15 Sliding Sliding friction is friction that acts on objects when they are sliding over a surface.

16 Sliding Example: You use sliding friction when you write with a pencil. The pencil lead slides easily over the paper, but there s just enough friction between the pencil and paper to leave a mark.

17 Sliding Can you think of other examples of sliding friction?

18 Rolling Rolling friction is friction that acts on objects when they are rolling over a surface.

19 Rolling Example: Rolling friction is much weaker than sliding friction or static friction. This explains why most forms of ground transportation use wheels, including bicycles, cars, 4-wheelers, roller skates, scooters, and skateboards.

20 Rolling Can you think of other examples of rolling friction?

21 6. Friction is Useful: Friction prevents our shoes from slipping on the pavement when we walk and stops car tyres skidding on the road. When you walk, friction is caused between the tread on shoes and the ground. This friction acts to grip the ground and prevent sliding.

22 6. Friction is Useful: Writing: hold your pen or your pencil; friction between your finger tips and the pen that keeps the pen from sliding out of your hand. Stopping: friction prevents cars, bicycles and other vehicles from skidding and helps them stop when the brakes are applied.

23 7. Friction is Harmful: Can cause burns- rope burn from tug of war Can cause blisterspair of shoes rubs against your skin

24 7. Friction is Harmful: Wears away surfacessole of your shoe, pencil eraser Can cause scrapes- if you trip and fall on the sidewalk

8. Reducing Friction Sometimes we want to reduce friction. For example, we use oil to reduce the friction between the moving parts inside a car engine.

25 8. Reducing Friction Sometimes we want to reduce friction. For example, we use oil to reduce the friction between the moving parts inside a car engine. The oil holds the surfaces apart, and can flow between them. The reduced friction means there is less wear on the car's moving parts, and less heat produced.

26 8. Reducing Friction Lubricate or oilsqueaky window Reduce force of weight pushing surfaces togetherheavy box Polish the surface to make it smootherbowling

27 Friction in Sports Name 3 sports where friction is helpful or useful. Explain!

28 Friction in Sports Name 3 sports where friction is reduced for better performance. Explain!

Basics, Types, Use and Applications

Basics, Types, Use and Applications 2015 by Brilliant Classes 2015 by Brilliant Classes Science : Physics Unit : Friction Friction : Basics, Types, Use and Applications The following topics are included