Force Identification

In this activity, students will learn to create a free body diagrams from more complex images. This is designed as a precursor to the interacting objects activity, designed to teach students to simplify their diagrams themselves rather than have the instructor do so for them.

Prior to class, students complete a reading assignment on types of forces and identifying forces. They then complete a reflective writing, summarizing the chapter and explaining the questions and problems they encountered during the reading.

Once in class, the instructor breaks the students into groups of 3-4. In their groups, students are tasked with finding an image of a stationary object online and sketching it, labeling all the forces acting on the object and drawing them as vectors. The groups then simplify their sketch to basic shapes (boxes, circles, etc.) and again label the forces. They then simplify their sketch further to a single dot with force vectors originating from it – this is introduced as a free body diagram. During this time, the instructor circulates about the room, providing assistance.

When students have completed their free body diagrams, the instructor chooses one of the examples to complete as an example in front of the class, demonstrating an efficient way of reducing the sketch to a simpler one then to a free body diagram.

This process is repeated for a moving object, then for two objects interacting (requiring two free body diagrams). This can be used to (briefly) hint at the upcoming concepts behind Newton’s second law (for the moving object) and Newton’s third law (for the interacting objects).

• Students learn to identify forces and simplify force diagrams, ending with a free body diagram.