Friction is a force that opposes the relative motion between two objects in contact. There are two main types of friction: static friction and kinetic friction. Friction can be both helpful and harmful. It allows for walking and braking a bicycle but also causes wear and tear over time. Friction depends on factors like the roughness and weight of surfaces, and it can be increased or decreased through these surface properties.

1. FRICTION

2. A force that opposes motion

3. Objectives… Explain why friction occurs. List the two types of friction, and give examples of each type. Explain how friction can be both harmful and helpful.

4. What is friction? Is a force that opposes motion between two surfaces that are in contact

6. When does friction occur? Friction occurs when two surfaces are in contact

7. Also… When a liquid or gas is pushed out of the way of a moving object

8. Why does friction occur? Because the hills and valleys of a surface are in contact with the hills and valleys of other surfaces, this produce friction.

10. Friction depends on… Roughness of surfaces and Force that objects are being pressed one against the other; or their weights

11. What increases friction? Rough surfaces And weight of objects

12. What does the amount of surfaces depend on? the amount of friction depends on how well the surfaces grip each other. Tyres on a road have very high friction (they don't slip), skates on ice have very low friction (they slip easily).

13. In a liquid or a gas For a solid object moving through a liquid or gas, the amount of friction depends on the shape and surface area of the object and the viscosity (thickness or thinness) of the liquid.

14. TYPES OF FRICTION KINETIC AND STATIC

15. What is kinetic friction? Is the friction between two moving surfaces

16. Sliding and Rolling

17. Static friction It occurs when a force is applied to an object but this object doesn’t move.

18. Static friction

19. Is friction good or bad? Friction can be good. When we walk we push backwards against the ground, the opposing force pushes us forwards. Without friction our feet would slip and walking would be impossible.

20. It is also good To stop your bicycle (brake system)

21. But sometimes is bad… Soil erosion caused by wind (friction of a fluid). Holes in your shoes, jeans. (friction of a solid) high friction Lack of friction is dangerous too, you may fall if the floor is very slippy.

22. Some ways to reduce friction

23. Some ways to increase friction

24. GO TO THIS LINK TO INCREASE YOUR KNOWLEDGE ABOUT FRICTION http://www.gcsescience.com/pfm32.htm