Frictional Force

Definition of Frictional Force

Frictional force refers to the force generated by two surfaces that contacts and slide against each other. These forces are mainly affected by the surface texture and amount of force impelling them together. The angle and position of the object affect the amount of frictional force.

Formula of Frictional Force

The maximum amount of friction force that a surface can apply upon an object can be easily calculated with the use of given formula.

Ffrict = µ • Fnorm

Frictional force

Types of Friction Force

1.Dry Friction: Dry friction is the force that competes with one solid surface gliding across another solid surface. Dry friction always opposes the surfaces sliding kin to one another and can have the effect of any opposing motion or causing motion in bodies. The most commonly used for dry friction is coulomb friction. This kind of friction can further be divided into static friction and kinetic friction.

2.Fluid Friction: Fluid friction takes place between fluid layers that are moving opposite to each other. This internal conflict to flow is named viscosity. In every day terms, the viscosity of a fluid is branded as its “thickness”. All actual fluids give some resistance to shearing and therefore are viscous. It is very helpful to use the concept of an ideal fluid which offers no resistance to shearing and so is not viscous.

Examples of Fluid Friction:

  1. When you drop the ball in full bucket of water, water splashes out of the bucket and is all because of buoyancy of fluid.

Problems on Friction Force


A 50N amount of force is applied to the 6 kg of box. If the coefficient of friction is 0, 3, what will be the acceleration of the box?


Fnormal =60N-40N=20N

Friction force is –  Ffriction=µ.Fnormal = 0, 3.20N=6N

Net force in –Y to Y = zero,

However, in –X +X direction net force is not zero