This Concept Builder is intended for use near the middle to late stages of a learning cycle on Newton's second law of motion. Most first-year Physics students quickly learn how to use Newton's second law equation to quickly calculate the net force from knowledge of the mass and acceleration. It takes a little longer before they become accustomed to analyzing a force diagram with known force values for individual forces and do the two-step analysis of determining the net force from the diagram and then the acceleration from the F
net = m•a equation. But in our experience, it takes even longer for Physics students to
work the same problem in reverse, using knowledge of mass and acceleration to determine the net force and then using the net force to calculate the value of an unknown force in a force diagram. It is this latter skill that this Concept Builder targets.
Every question in the Concept Builder includes a given mass and acceleration. Students are presented with the challenge of determining a set of north, south, east, and west vectors which will produce such an acceleration. They are provided with a force diagram and must
drag out force vectors on the diagram to a given magnitude in order to produce the specified acceleration. Once they tap on the Check Answer button, the motion of the mass is animated and feedback is provided.
This Concept Builder was intended as an in-class activity. After some early lab work, some discussion of the second law, and some practice using it in various problem-solving contexts, allow students an opportunity to interact with the questions. The Concept Builder includes three levels of difficulty. Teachers using the Concept Builder with their classes should preview the activity (or view the
Questions in the separate file) in order to judge which levels would be most appropriate for their students. The questions for each level are unique to that level. Our summary of the three levels is as follows: