Question

explain the concept of motion of a ball on a inclined plane

Answer 1

The main forces acting on the ball is gravity and friction.

All forces are then projected in 2 direction, first one is normal to the inclined plane and other parallel to it.

If you look into the forces parallel to the inclined plane, we have friction and mgsin(theta) (component of gravity force in the direction parallel to the inclined plane. The frictional force always act at the contact point of ball and inclined plane, while the gravity force acts at center of mass/gravity. Both the force are not in one line, they have a radius (R) distance between them, incase of a ball. This creates torque, which results in rotational motion; i.e. Rolling.