Question

define frictional force.

Answer 1

frictional force or friction is a force that is created when two surfaces move across each other. It slows down moving objects and reduces their Inertia

Answer 2

Friction is the resistive force that an object suffers while moving over a surface.
It acts opposite to the direction of motion or opposes motion.
 it is the reason for :
1.writing with chalk on a blackboard
2.walking
3.production of heat in heavy machinery
4. hand becoming hot while rubbing against thermocol