Frictional Force And Frictional Force Formula


It is the parallel component of the contact force between two bodies in contact. These forces are basically electromagnetic in nature. Friction can operate between a given pair of solids, between a solid and fluid or between a pair of fluid. the frictional force exerted by fluid is called viscous force. when two bodies slip over each other the force of friction is called kinetic friction. but when they do not slip but have a tendency to do so the force of friction is called the static friction.

Variation of friction
Variation of friction

Following points are important regarding friction-

  • If a body is at rest and no pulling forces acting on it the force of friction on it it is is zero.
  • If a force is applied to pull the body and it does not move the friction act which is equal to the magnitude and opposite in direction of the applied force.
  • friction is a self-adjusting force, father, as the body is at the friction, is called static friction.
  • If the applied force is increased the force of static friction also increases if the applied force exceeds certain maximum value the body starts moving this maximum value of static friction up to which body does not movies called the limiting friction.
  • static friction is a self-adjusting force, with an upper limit is called limiting friction.
  •  This limiting force of friction is found experimentally depend on the normal reaction. that is limiting friction is directly proportional to the normal contact force.

\(\begin{aligned}f_{L}\propto N\\ f_{L}=\mu _{s}N\end{aligned}\)

 Here \( \mu _{s}\) is a dimensionless constant and called the coefficient of static friction, which depends on the nature of the surface in contact.

  • If the applied force is further increased at the friction opposing the motion is called the Kinetic or sleeping friction. experimentally, it is well established the kinetic friction is less than the limiting friction and is given by

\(f_{L}=\mu _{k}N\)



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