Students can go through AP State Board 8th Class Physical Science Notes Chapter 2 Friction to understand and remember the concept easily.
AP State Board Syllabus 8th Class Physical Science Notes Chapter 2 Friction
→ Friction opposes the relative motion between two surfaces in contact. It acts on both surfaces.
→ Friction depends on the nature of the surface in contact.
→ For a given pair of surfaces, friction depends upon the state of smoothness of those surfaces.
→ Friction depends on how hard the two surfaces pressed together which is a normal force acting on the body.
→ Friction is independent of the area of contact.
→ Static friction comes into play when we try to move an object at rest relative to another surface or object.
→ Sliding friction comes into play when an object is sliding over another.
→ Sliding friction is smaller than static friction.
→ Friction is important for many of our activities.
→ Friction can be increased by making a surface rough.
→ The sole of the shoes and the tires of the vehicles are threaded to increase friction.
→ Friction is sometimes undesirable.
→ Friction can be reduced by using lubricants.
→ Friction produces heat.
→ When one body rolls over another body, rolling friction comes into play. Rolling friction is smaller than sliding friction.
→ In many machines, friction is reduced by using ball bearings.
→ When bodies move through fluids, fluids exert a frictional force called drag.
→ Fluid friction can be minimized by giving a suitable shape to bodies moving in fluids.
→ Friction: The force which opposes the relative motion of two surfaces of bodies that are in contact.
→ Static friction: The friction which comes into play when surfaces of the objects are at rest relative to each other.
→ Sliding friction: Sliding friction is the friction that comes into play when the surface of one object moves relative to the surface of another object.
→ Lubricants: The substances which reduce friction are called lubricants.
→ Ball bearings: The devices which reduce friction between rotating shafts of machine tools.
→ Drag: The frictional force exerted by fluids is called drag.
→ Fluid friction: Pressure exerted by fluids is called fluid friction.
→ Rolling friction: When one body rolls over the surface of another body, the friction offered ¡s called rolling friction.
→ Fluids: Liquids and gases are called fluids.
→ Leonardo Davinci (1452-1519):
- Leonardo Davinci was one of the first scholars to study friction systematically.
- He realized how important friction is for the working of machines.
- He focussed on all kinds of friction and drew a distinction between sliding friction and rolling friction.