Take a few pencils which are cylindrical in shape. Place them parallel to each other on a table. Place a thick book over it. Now push the book. You observe the pencils rolling as the book moves. Do you feel it easier to move the book in this way than to slide it? Do you think that resistance to the motion of the book has been reduced? Have you seen heavy machinary being moved by placing logs under it?
Motion of the book on rollers
b. The conclusion is that rolling friction is less than .