FRICTION Prepared by: Mr. Navneet Gupta Lecturer (Government Polytechnic College, Ambala City)

A force that opposes motion

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.

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

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

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

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.

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

What increases friction? Rough surfaces And weight of objects

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).

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.

TYPES OF FRICTION KINETIC AND STATIC

What is kinetic friction? Is the friction between two moving surfaces

Sliding and Rolling

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

Static friction

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.

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

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.

Some ways to reduce friction

Some ways to increase friction

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