This classic demonstration is done in two steps. This first time the demonstration is meant to fail. The second time the demo succeeds.
1. (This one fails on purpose): The tablecloth has a plate and silverware epoxies to the red and white-checkered tablecloth. This is a gag where the professor piles plastic food on the plate and then, when the tablecloth is jerked out the plastic food bounces off of the blackboard. Uncertain expressions with a worried look help set the tone. Students would rather see a demo fail than succeed. Pull slightly upward away from the table. Try to look disappointed and then show them the tablecloth with the plate glued to it to show that it was a gag but reassure them that you can pull a tablecloth out from under the dinner setting.
2. (This one that works): The red tablecloth is made from a static free polyester material that is also low friction. The concept is inertia and the wood block provides some. Pile on top of the block several pieces of Styrofoam until it is a foot or so high tower. Tug on the tablecloth a few times so that it wobbles and looks quite precarious. Add one more piece of Styrofoam to the already wobbling tower. Then when you are ready to pull it the force must be downward and away from the table. A quick snapping action is needed.