Page 1 - Lesson Notes
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SAI INTERNATIONAL SCHOOL
                                                          Class8
                                                     Lesson Notes
                                                   Subject-Physics
                                                       CH-Friction
                            Subtopic-Methods to increase and decrease friction

               Methods to increase friction:
               1.  Make the surface rough: Grooves are made in the shoe soles to increase friction.
                    Gymnast apply some coarse substance on their hands to increase friction.
               2.  Press the surfaces harder against each other: while walking on a slippery surface,
                    we need to place our feet carefully and press it hard against the floor to avoid
                    slipping.

               Methods to decrease Friction:
               1.  By making surface smooth: The slides in the park are polished to make it smooth
                    and easy to slide.
               2.  By applying lubricants: Oil is poured in the machines to reduce friction.
               3.  By using wheels/ ball bearings: Wheels are provided in suitcase to reduce friction
                    while pulling. Ball bearings are used between machine parts which slide over each
                    other to reduce friction.

               Note:
                 Lubricant is a substance which is used between the surfaces of the moving objects
                    to reduce friction.
                      They  reduce  friction  by  filling  up  the  irregularities  and  making  a  thin  layer
                        between the surface. Thus preventing the interlocking of irregularities.
                      Eg: oil, grease, graphite powder
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