Friction

Friction

Project Type: Presentation (ppt)

Downloads: 0 - 10 Wednesday 15th March 2017 Report

Friction - Overview

------------ PAGE 1 ------------ FRICTION ------------ PAGE 2 ------------ A force that opposes motion ------------ PAGE 3 ------------ Objectives… ƒÞ Explain why friction occurs. ƒÞ List the two types of friction, and give examples of each type. ƒÞ Explain how friction can be both harmful and helpful. ------------ PAGE 4 ------------ What is friction? ƒÞ Is a force that opposes motion between two surfaces that are in contact ------------ PAGE 5 ------------ contact ------------ PAGE 6 ------------ When does friction occur? ƒÞ Friction occurs when two surfaces are in contact ------------ PAGE 7 ------------ Also… ƒÞ When a liquid or gas is pushed out of the way of a moving object ------------ PAGE 8 ------------ Why does friction occur? ƒÞ Because the hills and valleys of a surface are in contact with the hills and valleys of other surfaces, this produce friction. ------------ PAGE 9 ------------ friction. ------------ PAGE 10 ------------ Friction depends on… ƒÞ Roughness of surfaces and ƒÞ Force that objects are being pressed one against the other; or their weights ------------ PAGE 11 ------------ What increases friction? ƒÞ Rough surfaces ƒÞ And weight of objects ------------ PAGE 12 ------------ What does the amount of surfaces depend on? ƒÞ 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). ------------ PAGE 13 ------------ In a liquid or a gas ƒÞ 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. ------------ PAGE 14 ------------ TYPES OF FRICTION ƒÞ KINETIC AND ƒÞ STATIC ------------ PAGE 15 ------------ What is kinetic friction? ƒÞ Is the friction between two moving surfaces ------------ PAGE 16 ------------ Sliding and Rolling ------------ PAGE 17 ------------ Static friction ƒÞ It occurs when a force is applied to an object but this object doesn’t move. ------------ PAGE 18 ------------ Static friction ------------ PAGE 19 ------------ Is friction good or bad? ƒÞ 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. ------------ PAGE 20 ------------ It is also good ƒÞ To stop your bicycle ( brake system) ------------ PAGE 21 ------------ But sometimes is bad… ƒÞ Soil erosion caused by wind ( friction of a fluid). ƒÞ Holes in your shoes, jeans. ( friction of a solid) high friction ƒÞ Lack of friction is dangerous too, you may fall if the floor is very slippy. ------------ PAGE 22 ------------ Some ways to reduce friction ------------ PAGE 23 ------------ Some ways to increase friction ------------ PAGE 24 ------------ GO TO THIS LINK TO INCREASE YOUR KNOWLEDGE ABOUT FRICTION ƒÞ http:// www. gcsescience. com/ pfm32. htm
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