Name: Necessity of Friction
Uploaded: 2019-07-19
Duration: 4 min 40 s
Description: This video enables students to learn about friction, friction used in routine activities, loss of energy in the form of heat due to friction.

Question

A book placed on the surface of a table. The book is pushed in one direction. Draw the forces acting on the book and explain.

Accepted Answer

When a book placed on the surface of a table is pushed in one direction, the forces acting on the book are as follows:

(i) Weight of the book ( $W$ ) or gravitational force acting vertically down.
(ii) Normal force ( $N$ ) or reaction force applied by the horizontal floor (table) vertically up.

As there is no change in motion of the book along the vertical direction, the net force acting on the book in the vertical direction is zero.

That is, $W - N = 0 W = N .$

In the horizontal direction, the speed of the book is changing continuously. Its speed is decreasing gradually in the horizontal direction i.e., the book has acceleration opposite to the direction of motion.
The floor applies a force on the book against its motion. Similarly, the book also applies the same amount of force on the floor (table) in the opposite direction. Here it is clear that the floor (table) is at rest. Hence, the net force acts in the direction of the force applied by the floor (table) on the book. The force applied by the floor on the book is friction.

A book placed on the surface of a table. The book is pushed in one direction. Draw the forces acting on the book and explain.

Important Questions on Friction

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