Friction

Objectives:

1.    Describe the nature of forces.

2.    Explain how force is related to motion.

3.    Identify friction as the force that opposes motion.

4.    Name & describe the three types of frictional force.

Web Resources:

Objectives:

1.    Describe the force of friction on stationary and moving objects.

2.    Be able to distinguish between the three different types of friction.

3.    Identify the four main factors that contribute to friction.

Notes:

It is important to remember that a force is a push or a pull.  Forces can give energy to an object and cause it to move, forces can stop the movement of an object, and forces can change the direction of an object.  These aspects of force were described by Newton in his second law of motion.  But what else can force do?  The force of friction (which is always present on Earth) can keep an object stationary or can slow it down once it is moving.

(www.abc.net.au/.../2000/transport/ land/img/friction.jpg)

FRICTION:

Friction is a force that opposes motion.  When two objects are in contact, friction is acts in a direction opposite to the motion of the object.

(www.visionengineer.com/ ref/friction.gif)

3 types of friction:

• Sliding friction

• Rolling friction

• Fluid friction

SLIDING FRICTION:

The type of friction created when 2 solid surfaces slide over each other.

Factors:

• Weight of the moving object

• Types of surfaces

• Texture of the two surfaces

• Temporary bonding of the two surfaces

ROLLING FRICTION:

(www.railway-technology.com/ .../kluber/image2.jpg)

• Friction created when an object rolls over a surface.

• Opposes motion less than sliding friction.

FLUID FRICTION:

• Created when an object moves through a fluid.

• Fluid can be gas or liquid

• Opposes motion less than sliding

Lubrication is how fluid friction used to reduce the opposing force of sliding and rolling friction?