Recognizing Forces: Does the Floor Know When You Put on Weight?
This beginning Physics lesson introduces students to forces and free body diagrams (i.e. force diagrams). Rather than modeling forces in abstract situations, the lesson challenges students to develop diagrams that accurately describe the forces acting on them. After introducing the force of gravity and normal force, students build their own free body diagrams using the data provided by a bathroom scale. Students will build three free body diagrams providing formative assessment opportunities for you and your students.
The lesson confronts the following student misconceptions:
The scale measures the force of gravity. The scale actually reads the normal force pushed up onto you by the scale.
The normal force always equals the force of gravity. In fact, they are not always equal, as students will see.
Through this lesson, students will investigate real forces while learning how to develop visuals to represent those forces. The lesson can be completed in one 45-60 minute period, with no materials required other than a bathroom scale. There are few prerequisite beyond a basic familiarity with mass and using units.