AP 8th Class Physical Science Notes Chapter 2 Friction
→ 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.
→ Friction : Friction opposes the relative motion between two surfaces in contact. It acts on both the surfaces.
→ Interlocking : When the irregularities of any two objects came in contact and get interlocked.
→ Lubricants : The substances which reduce friction are called lubricants.
→ Rolling friction : When one body rolls over the surface of another body, the resistance to its motion is called rolling friction.
→ Sliding friction : Sliding friction comes into play when an object is sliding over another.
→ Static friction : The friction which comes into play when surfaces of the objects are at rest relative to each other.
→ Fluids : Liquids and gases are called fluids.
→ Frictional force opposes the relative motion between two surfaces in contact. It acts on both the surfaces.
→ Frictional force acts in the opposite direction of the applied force.
→ Frictional force depends on the nature of surfaces in contact and on the areas of contact. Friction force is of three types.
→ Static friction, sliding fiction, rolling friction.
→ For a given pair of surfaces friction depends upon the state of smoothness of those surfaces.
→ Friction depends on how hard the two surfaces press together.
→ Static friction comes into play when we try to move an object at rest.
→ 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 tyres of the vehicles are threaded to increase friction.
→ Friction is sometimes undesirable.
→ Friction can be reduced by using lubricants.
→ 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 cap be minimised by giving a suitable shapes to bodies moving in fluids.