What Is Meant By Rolling Friction? Is Rolling Friction Greater Than Sliding Friction?

The type of friction which is produced between the two bodies when the surface of one body moves by sliding against the surface of the other body. It is our common observation that a body with wheels faces less friction as compared with the bodies of same size but which are without wheels. Its reason is that the rolling friction is far less than the sliding friction and this is the reason that the invention of wheel is considered to be a revolutionary invention even today. It is because of the fact that it has brought much convenience in transportation. When a wheel moves on a smooth surface, it has to connect with the surface only at a single point. Since there is no relative motion between the two surfaces at this point. Therefore, the sliding friction is almost zero. However, practically, the wheel is compressed a little temporarily at the connect point of the two surface under stress. This little sliding friction is called the rolling friction. The rolling friction is much less than the sliding friction. It is almost a hundred times less than that of sliding friction. Therefore, at the points of machines which have to slide against each other, ball bearings are used, which converts the sliding friction into rolling friction. Wheels are fixed under heavy suitcases, deep freezers and trollies due to which they become easier to move.

Yes it is. Rolling friction is always greater than sliding friction. In sliding friction all the molecules are     pushed but in rolling friction all  molecules are crossed.