Rotating Platform

An object placed on a rotating platform experiences a force directed away from the centre known as the Centrifugal Force. All of us feel this force when we are on a rotating system like a merry-go-round or on a rotating platform like the one we have here. On account of this force a ball rolled or thrown to another person on the rotating platform traverses in a curved path. The curvature depends on the speed of the ball as well as that of the platform. Also, the ball curves away in a direction opposite to the direction of the rotation of the platform.

Set the platform into rotation and roll a ball on it. The path of the ball appears to be more or less linear for a person who is standing outside the rotating system. But for a person who is standing on the platform, the path of the ball is curved.

This is because the ball rolling on a rotating platform experiences a centrifugal force i.e, it experiences a force always pointed away from the centre. This force is coming up due to the friction between the surfaces.

The ball is initially given a velocity i.e, speed with direction. This direction of the ball gets altered due to the influence of this centrifugal force. So, the ball takes a curved path.

The curvature depends on the speed at which the ball is rolling. A ball that is rolled fast takes a less curved path where as the one that is rolled slow takes a more curved path.

The path taken by the ball is the result of the net force acting on that ball during all the instants of its motion on the platform. The ball is initially imparted with a force in the linear direction and since the platform is rotating, there is a force pointing away from the centre. The direction of the resultant of these two forces is the direction of the motion of the ball.

Therefore if the initial applied force is more, the direction of the force is less deviated from the initial and hence a less curved path and viceversa.

A group of students can easily visualize this effect by two of them sitting in diametrically opposite positions on the platform. The ball rolled by one student will not reach the other when the platform is rotating.

The ball can be wrapped with a wet cloth and then rolled on the rotating platform. This leaves a track which depicts the curved path of the ball.