Normal forces are named so because they demonstrate a stable, consistent force between two objects. Examples of normal force include a book resting on a table or a person leaning against a wall. In either case, both objects are exerting force on one another to maintain a stable relationship. To get your students thinking about normal force, have each take out a pen and a piece of paper. Students have five minutes to list as many normal forces as they can find in the room. The student with the longest list wins and gets a small prize. Expand this game to the schoolyard, school halls or other rooms in the school, if you have the capacity to do so.
Have each student bring an expendable object to school, such as a rock, chicken's egg or bouncy ball. Each student must bring a different item for the sake of experiment. Students weigh and record the physical properties of their object to start. Next, take students and to the highest floor of the school and position them at a window one-by-one. Once you've made sure there's nothing going on beneath you, each student drops their object out of the window, and a student stands below and times how long it takes each object to drop. Students observe the effects of gravity on objects of different weights and masses.
Give students a Hot Wheels toy car and access to books, plywood, blocks or other stacking materials. Give each student a flat plywood board for the base of the ramp. Each student has access to the same number and type of materials and is asked to build a ramp that will allow the car to go fastest and farthest to cross the finish line and win the race. A finish line is set up a few yards ahead, and students are given 10 minutes to build the best ramp. On the count of three, students roll their cars down the ramp and see who wins. Next, students are given five pennies and asked to tape between one to five of them to the tops of their toy cars. Ask them to hypothesize whether this will make the car go faster or slower. Students race again with the pennies and record who wins, and then explain why.
For safety, use a large bouncy ball instead of a traditional volleyball for this game. Explain to your students that when you call out different words, you expect different actions. When you call out "Normal force," the student the ball has been hit to will hit the ball again to another random student. When you call out "Gravity," the students should let the ball fall to the ground. When you call out "Third Law," the student standing next to the student the ball is coming to attempts to block that student from hitting the ball by applying equal force against his hit. When you call out "Applied force," the student attempts to hit the ball hard so that the next student can't return it. When you call out "Inertia," the student catches the ball and holds it, and then waits for you to call the next move. Students who fail to act on command are out, just like in "Simon Says." The winner is the student who obeys commands the longest.