Facts about friction

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Ever tried skating on ice? If yes, you would probably know by now that ice skating is the easiest way to slip and fall on your back without even trying!

Try the same on a well laid graveled road and it seems almost impossible to slip unless there’s a slippery fluid lubricating the surface.

What is responsible for this major difference between the two surfaces? Well, the answer is simple. Friction!
What is friction? Read on to find out.

1. What is friction?

Friction is defined as the opposing force that comes into play when two surfaces slide over each other. It reduces the net force and acceleration of the object.

2. What causes friction?
Friction is a result of the irregularities present on the surfaces in contact. During motion, these irregularities rub against each other resulting in heat energy that is visible as friction. Even surfaces that appear smooth on the outside may show irregular surfaces when viewed at microscopic levels.

3. Is it a directional force?
Friction tends to act in the direction opposing motion. An object moving up experiences a frictional force in the downward direction and so on. Thus for an object to move, a force equal to the frictional force must be applied so that the two forces cancel out resulting in motion.

4. Static friction and sliding friction.
Static Friction: Static friction is that force that exists to oppose the motion of an object till a threshold level is reached where in applied force exceeds the frictional force. It thus exists between a stationary object and its contacting surface.
Sliding Friction: Sliding friction or kinetic friction is that opposing force that comes into play when the two objects in contact move relative to each other.
In general, static friction is greater than sliding friction.

5. The relation between friction and mass of an object.
The frictional force depends on the force exerted perpendicularly to the surface of an object. While mass does not directly alter friction, a change in mass of the object results in a corresponding change in the normal force exerted thus changing the value of friction.

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6. Frictional force is independent of the speed of an object.
The frictional force on an approximation is said to be independent of speed. A car skidding at high speed and that skidding at low speed have an almost similar value of frictional force acting on them. While this is true, the frictional force experienced by a car moving at a higher speed as air resistance is much greater than that experienced by a car moving at a slower speed.

7. Frictional force is independent of the area of contact.
We have all observed that the tires on some vehicles are abnormally wider or narrower than the rest. Well, irrespective of the surface area in contact the frictional force experienced by all tires is in fact the same and only depend on the type of material.
Wider tires only help reduce wear and tear.

8. Friction also exists in liquids and gases.
Friction as an opposing force may also be experienced in fluids.
Friction in liquids: Viscosity or the ease with which a liquid flows is dependent on the frictional force acting between the molecules of the fluid layers in contact.
Friction in gases: Air resistance or air drag is one of the most common forms of friction in gases that is widely experienced at relatively higher speeds of motion. To overcome this force of friction, vehicles have a streamline design to help them cut across the air drag.

9. The different types of friction.
The two types of friction are: Dry friction and lubricated friction.
Dry friction: Opposing force that resists motion between two solid surfaces in contact.
Lubricated friction: Opposing force that resists motion between two solid surfaces in contact with a fluid layer between them.

10. Reducing friction.
Friction may be reduced by use of lubricants that tend to decrease coefficient of friction between the two surfaces in contact thus enabling their movement. Lubrication is achieved by using materials like oil and grease.

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