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.
For example, with the Hero Engine, water streams in one direction and the can rotates in the opposite direction. With the truck and marbles' activity, the truck goes in one direction while the cardboard goes in the opposite direction. As the person steps off the skateboard, they exert an action force on the board, making it go in the opposite direction. Pupils found that they could not pull on opposite ends of the Demo Spring Scales with different amounts forces. As they pulled, the scales always read the same force.