On an incline, the force causing the ball to move downwards would be gravity. Additionally, the component of gravity causing this ball to move downwards would be mgsintheta. Hope this helps!
If a body s placed on an inclined plane, then there are two component of weight of the body . One component is along the plane and the other is perpendicular to the plane.
Let there is an inclined plane which makes an angle theta with the horizontal. A body of mass m is placed on the inclined plane.
The component of weight along the plane is m g Sin theta
The component of weight perpendicular to the plane is m g Cos theta.
So, the force acting on the ball to move downhill is the force acting along teh plane. That means m g Sin theta.
