We were discussing the importance of friction
i.e. positive and
negative effects of friction, classifications
of friction and coulomb's law of dry friction with the help of
our previous post.

###

Now, we will be interested further to understand here
few guidelines for solving frictional problems. We will see here few
important points that we need to keep in mind during solving the problems
related with friction.

###
**Guidelines for solving friction problems
in mechanics**

Laws of friction will be valid only at the moment when
motion is impending. Impending motion refers to the state just before body surface
starts to slip.

The reaction force at the surface can be resolved into
two forces i.e. normal and tangential.

When the motion is not impending, the frictional force
can be determined only by using the equilibrium equations.

We need to start to solve the frictional problem by
indicating the frictional forces as unknowns with suitable symbols f

_{1}, f_{2}etc.
Unlike other free body diagram problems, any direction
could not be considered for frictional forces. It should always be such that it
opposes the motion.

Analyse whether motion is impending or not. If motion
is impending, replace f

_{1}, f_{2}etc with µ_{s}x Normal load. Otherwise, we will leave the unknowns as it is and will determine them using equilibrium equations.
Frictional force reduces as motion commences because
of the reduced meshing and adhesion of the surfaces.

Friction coefficient will be dependent on the quality
of surface of finish.

Therefore, we have studied here the various guidelines
for solving frictional problems. Further we will find out another concept in
friction i.e. rolling resistance with the help of our next post.

Do 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 from www.hkdivedi.com.

We will find out now the concept of rolling resistance
in our next post.

### Reference:

Engineering Mechanics, By Prof K. Ramesh

Image courtesy: Google

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