Allow the ball provided to roll down from the starting point marked. Observe the ball till it falls into the bottom hole.

What did you observe? 
The ball moves slower at the outer circles but when it comes closer to the centre, its angular speed is very high

The science behind it :
The motion of ball with differing angular speed illustrates Keppler’s Second law of planetary motion. This law states, “The line joining the sun and planet sweeps out equal areas in equal times”. So the planet moves faster when it is nearer to sun. Thus, a planet executes elliptical motion with constantly changing angular speed as it moves about its orbit.