Page 9 - Demo

FRICTION 155 KEYWORDSBALL BEARINGDRAGFLUID FRICTIONFRICTIONINTERLOCKINGLUBRICANTSROLLING FRICTIONSLIDING FRICTIONSTATIC FRICTION WHAT YOU HAVE LEARNT%u0001 Friction opposes the relative motion betweentwo surfaces in contact. It acts on both thesurfaces.%u0001 Friction depends on the nature of surfaces incontact.%u0001 For a given pair of surfaces friction dependsupon the state of smoothness of thosesurfaces.%u0001 Friction depends on how hard the two surfacespress together.%u0001 Static friction comes into play when we try tomove an object at rest.%u0001 Sliding friction comes with play when anobject is sliding over another.%u0001 Sliding friction is smaller than static friction.%u0001 Friction is important for many of our activities.%u0001 Friction can be increased by making a surfacerough.%u0001 The sole of the shoes and the tyres of thevehicle are treaded to increase friction.%u0001 The friction is sometimes undesirable.%u0001 Friction can be reduced by using lubricants.%u0001 When one body rolls over another body, rollingfriction comes into play. Rolling friction issmaller than the sliding friction.%u0001 In many machines, friction is reduced byusing ball bearings.%u0001 Fluid friction can be minimised by givingsuitable shapes to bodies moving in fluids.Exercises1. Fill in the blanks:(a) Friction opposes the _____________ between the surfaces in contactwith each other.(b) Friction depends on the _____________ of surfaces.%u00a9 NCERTnot to be republished