question_answer

(i) In the experiment to find the relationship between weight of the rectangular block lying on a horizontal table and the applied force, a boy observes that the block begins to slide over the table when the spring balance reading is 10 N. If the reading of the spring balance is 5 N, then what will be the force of friction that will come into play? (ii) When a body actually begins to move over the surface of another, name the frictional force which will come into play?    

Answer:

(i) 5 N. Because before the applied maximum force to just move the block, the applied force has been exactly balanced by the force of friction which is acting at the interface of the block and the horizontal surface of the table. The block remains at  rest.                                                                                                                                                                       (1) (ii) Kinetic friction comes In to play. It is because when the limiting friction is overcome by the applied force, the body begins to move and the limiting friction is converted into kinetic friction.                                                               (1)