Alternative to Table Cloth Pull
To demonstrate that the ball will remain in the same relative position because the force acting on it is not great enough to overcome the balls inertia.
Stand with metal rod
Small piece of cardboard
Set the stand on a flat surface and then place the cardboard on top of the metal rod. Then place the steel ball on top of the cardboard directly over the metal rod. Pull the plastic spring back and release it should knock the cardboard out from under the ball and the ball should fall into the indentation in the metal rod.
It is extremely important that the surface be completely level or the ball will keep falling off the metal rod. It may also be a good idea to put the cardboard on a little off center to make it easier to knock off, the ball should have the weight necessary to keep the cardboard from falling off. Also make sure that you practice a few times as this demonstration can be difficult and frustrating, also you need to find the correct distance to pull the plastic spring back so that it has the energy to knock off the cardboard but not hit the steel ball. Also the platform may move causing the ball to fall so it is a good idea to use your hand to hold it down.