Final answer:
When the ball rolls from the ruler to the barrier, there are several forces acting on the ball including gravity, normal force, friction, and the force exerted by the barrier.
Step-by-step explanation:
When the ball rolls from the ruler to the barrier, there are several forces acting on the ball. First, there is the force of gravity pulling the ball downwards. There is also the normal force exerted by the surface on the ball, which is perpendicular to the surface. Additionally, there may be a frictional force between the ball and the surface it is rolling on. Finally, if the ball collides with the barrier, there would be a force exerted by the barrier on the ball and an equal and opposite force exerted by the ball on the barrier (Newton's third law of motion). Each of these forces can affect the motion of the ball in different ways.