We were discussing the importance of friction i.e.Â positive
and negative effects of friction,Â classifications
of friction,Â coulomb's law of dry frictionÂ and
guidelines for solving frictional problems with the help of our previous
post.Â Â

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Now, we will be interested further to understand here the
basic concept of rolling resistance or rolling friction, definition of rolling resistance, formula or expression for rolling resistance and factors that contribute to the rolling resistanceÂ with the help of this
post.

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**Rolling resistanceÂ **

Rolling resistance is basically defined as the force
resisting the motion, when a body such as ball, wheel, automobile tyre rolls along the surface of another body.Â

Deformation at the point of contact will develop the
resistance to rolling. This resistance will be an entirely different phenomenon
from that of dry friction.Â

In analogy with sliding friction, rolling resistance
will be expressed as a coefficient of rolling resistance multiply by the normal
force.Â

There will be no slipping or impending slipping in the
interpretation of rolling resistance.Â

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**Formula or expression for rolling resistanceÂ **

The expression for rolling resistance could be written as mentioned belowÂ

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**Fr = c x WÂ **

Where,Â

Fr = Rolling resistance or Rolling friction (N)Â

c = Rolling resistance co-efficient or co-efficient of rolling friction i.e. CRFÂ

W = Normal force (N)Â

Rolling resistance co-efficient or co-efficient of rolling friction i.e. CRF is a dimensionless.Â Â

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**Factors that contribute to the rollingÂ resistance**

Factors that contribute to rolling resistance are the
deformation of the wheels, the deformation of the roadbed surface, surface
adhesion, wheel diameter, speed, load on the wheel, sliding and relative micro-sliding
between the surfaces of contact.Â

For example, you can see that a rubber tyre such as
automobile car will have higher rolling resistance on a paved road as compared
with a steel railroad wheel such as a train wheel on a steel rail.Â

Automobile car running on a road will have higher
rolling resistance because its tyre wheel will be soft. On the other hand,
train steel wheel running on rail track will have relatively lower rolling
resistance as its wheel will be quite hard as compared with the tyre wheel.Â

We must note it down here a very important point that
rolling friction has the least value. Rolling resistance or rolling friction
has led to the development of ball and roller bearings.Â

You can see here the detailed post based on the basics
of bearings.Â

Therefore, we have seen here the basics of rolling
resistance or rolling friction with the help of this post. We have also
introduced here the bearings which is basically the result of research to
reduce the rolling resistance.Â

DoÂ you have any suggestions? Please write in
comment box and also drop your email id in the given mail box which is given at
right hand side of page for further and continuous update fromÂ www.hkdivedi.com.Â Â

### Reference:Â Â

Engineering Mechanics, By Prof K. RameshÂ Â

Image courtesy: GoogleÂ Â Â Â

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