CBSE Class 8 Science Chapter 12 Friction Revision Notes
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Friction comes into play when we rub two surfaces. It can be wiping a cloth across a table to wipe it clean or your boots as they skid along ice or snow. In other words, friction is the resistant force to motion when one object rubs against another. Anytime two objects rub against each other, they cause friction. Friction works against the motion and acts in the opposite direction.
Types of friction:-
● Static friction: A frictional force that comes into action before the start of the motion of an object is called static friction.
● Sliding friction: When an object slides over another surface, the frictional force that comes into action is sliding friction.
● Rolling friction: The frictional force exerted by a body when it rolls over a surface is called rolling friction.
● Fluid friction: The frictional force exerted by fluids when objects move through them is called fluid friction.
Factors affecting friction:-
Friction depends on the nature of surfaces in contact. For a given pair of surfaces, friction depends upon the state of smoothness or roughness of those surfaces.
● The force of friction is greater if a rough surface is involved.
● Friction is caused by the irregularities of the two surfaces in contact.
● Irregularities of the two surfaces lock them with one another.
● In order to move any surface, a force needs to be applied to overcome interlocking.
● Rough surfaces have a large number of irregularities.
● Friction depends on how hard the two surfaces pressed together.