Naturally, the small pupil loses. Then have the four larger pupils stand on the giant skateboard, and have pupils predict the outcome of the tug of war. The class discusses what happened and why. Then a general rule or law is produced through total group participation. Groups write up their thoughts about each station and post their group's conclusions on the chalkboard.
Selected persons report orally before the class.
Attach a personal fan to a Pasco dynamics cart with tape. Turn it on. The class concludes that the action of the blades on the fan is the cause of the cart gliding in the opposite direction. This gliding is the reaction force. Pupils form the general law which states that actions take place in pairs with reactions.