Frictional force is the force that opposes the motion of an object when it is in contact with another surface. It is caused by the microscopic irregularities in the surfaces of the two objects rubbing against each other.
Frictional force can be calculated by multiplying the coefficient of friction (μ) between the two surfaces by the normal force (N) exerted on the object by the surface it is in contact with. The formula is F = μN.
The magnitude of frictional force depends on the nature of the two surfaces in contact, the normal force between them, and the coefficient of friction. Other factors that can affect frictional force include the speed of the object and the temperature of the surfaces.
Frictional force acts in the opposite direction of motion, slowing down or stopping the movement of an object. It also causes objects to slide or roll, rather than move in a straight line, and can cause objects to heat up due to the energy lost as heat during friction.
Frictional force can be reduced by using lubricants, such as oil or grease, between the two surfaces in contact. Smooth surfaces also have less frictional force compared to rough surfaces. Additionally, reducing the normal force or using materials with low coefficients of friction can also decrease frictional force.