Concetti Chiave
- Friction is the resistance to motion occurring between contacting materials or media, present in solids, liquids, and gases.
- Static friction prevents motion between dry and clean solid surfaces and must be overcome to initiate movement.
- Sliding or kinetic friction is the resistance encountered when solid surfaces slide over each other, requiring less effort to maintain motion than to start it.
- Rolling friction resists motion when one solid object rolls over another, such as a ball or wheel on a surface.
- Fluid friction resists the flow of liquids and gases, opposing their movement.
The resistence present to motion between contacting materials or media.
It occurs in all types of media: solids, liquids + gases.
- Static friction: the force that prevents motion between dry + clean contacting solid surfaces, to start motion between the surfaces static friction must be overcome.
- Sliding or kinetic friction: the resitive force between dry and clean solid surfaces sliding over each other. Static friction is always greater than sliding friction. It takes less effort to keep a sliding object moving than it does to set it in motion.
- Rolling friction: the force that resists relative motion between two solid objects when one or both roll over the surface of the other, example: a ball or wheel rollingover a hard surface.
- Fluid friction: the force that resists the flow of liquids and gases.
Properties of Friction
Friction depends on the physical and material properties of the contacting surfaces. It is:
-always in a direction opposite the motionor a force attempting to produce motion;
-directly proportional to the load;
-indipendent of the surface area;
-indipendent of the sliding speed.
The load is the applied force perpendicular to the contact surface that presses them together.
The load on a horizontal surface is equal to the weight of the object.
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