Question

An example of rolling friction is:
A. Using oil to lubricate
B. Skateboard moving on wheels
C. Dragging your sister across floor on a blanket
D. A fish swimming through ocean

Answer 1

- Hint: Rolling friction is the resistance offered by a rough surface to any object which tries to roll on it. Rolling friction inversely proportional to smoothness of surface means if smoothness of surface increases rolling friction decreases. Wheels or any rolling body experience this resistance or drag.

Complete step-by-step solution -
A. The first option is incorrect because lubrication has nothing to do with the nature of the friction. Lubricating oils reduce any type of friction.
B. The second option is the correct one. A rider should push the skateboard to keep it running. The rolling of the wheels over a rough surface offers resistance to the motion. Hence, it is an example of rolling friction.
C. The third option is wrong because dragging is simply sliding on a surface. The person being dragged, does not roll on the surface.
D. A fish does not roll through the water while rolling. So, there is no rolling friction and the fourth option is wrong.

Note: Rolling friction is absent in systems where there is no rotational motion although other types of friction may be present.
Sometimes we can mix it with the concept of sliding friction but both are different. In sliding friction there is motion when two surfaces rubbed each other.