This Concept Builder will serve as a useful pre-cursor to solving Newton's Second Law problems. Students will gain considerable practice calculating the net force from individual force values and determining the acceleraton from a combination of individual force values and object mass. Most students will be able to do the mathematical manipulatives in their head. They will just need a solid understanding of how to do it.  Every question in the Concept Builder falls into one of two categories: (1) Rank the net force of the given objects from most negative to most positive, or (2) Rank the acceleration of the given objects from most negative to most positive. The number of given objects to rank depends upon the difficulty level. There are three difficulty levels. The Apprentice Level includes four objects in each ranking task. The Master Level includes six objects in each ranking task. And the Wizard level includes eight objects in each ranking tasks.

The Concept Builder is a ranking task activity. Such ranking task activities have become popular in the Physics teaching community, having been popularized for some time by the TIPERs (Tasks Inspired by Physics Education Research).  This Concept Builder will help students gain a better intuition for the relationship between acceleration, net force and mass. The activity can be used at about any time during a learning cycle on Newton's second law. But we recommend that it be used quite early and prior to the use of the formula as a tool for algebraically solving physics word problems.

This particular Ranking Task activity was inspired by a post on Twitter by Brian Frank and has been implemented here with his permission. Brian is a Professor of Physics at Middle Tennessee State University. You can learn more about Brian's use of this and similar activities and other approaches to Physics teaching at his blog - Teach. Brian. Teach. (https://teachbrianteach.com) or by following him on Twitter (@brianwfrank). Thanks to Brian for inspiring this idea.

This Concept Builder was intended as an in-class activity. After some early lab work, some discussion of the second law, and some discussion of the relationships between acceleration and net force and mass, 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. Our summary of the three levels is as follows:

We can imagine it being profitable to allow students to make judgements as to what level to begin with and to progress from easier to more difficult levels. 

In order to complete a level, a student must correctly analyze each question at that level. If a student's analysis is incorrect, then the student will have to correctly analyze the same or very similar question twice in order to successfully complete the level. This approach provides the student extra practice on questions for which they exhibited difficulty. As a student progresses through a level, a system of stars and other indicators are used to indicate progress on the level. A star is an indicator of correctly analyzing the question. Once a star is earned, that question is removed from the que of questions to be analyzed. Each situation is color-coded with either a yellow or a red box. A red box indicates that the student has incorrectly analyzed the question and will have to correctly analyze it twice before earning a star. A yellow box is an indicator that the question must be correctly analyzed one time in order to earn a star. Once every question at a level has been analyzed, the student earns a trophy which is displayed on the Main Menu. This system of stars and trophies allows a teacher to easily check-off student progress or offer credit for completing assigned levels.

The most valuable (and most overlooked) aspect of this Concept Builder is the Help Me! feature. Each question group is accompanied by a Help page that discusses the specifics of the question. This Help feature transforms the activity from a question-answering activity into a concept-building activity. The student who takes the time to use the Help pages can be transformed from a guesser to a learner and from an unsure student to a confident student. The "meat and potatoes" of the Help pages are in the sections titled "How to Think About This Situation:" Students need to be encouraged by teachers to use the Help Me! button and to read this section of the page. A student that takes time to reflect upon how they are answering the question and how an expert would think about the situation can transform their naivete into expertise. 

 

 

There are numerous resources at The Physics Classroom website that serve as very complementary supports for the Net Force Ranking Tasks Concept Builder. These include:

Additional resources and ideas for incorporating Net Force Ranking Tasks into an instructional unit on Newton's Laws can be found at the Teacher Toolkits section of The Physics Classroom website.  Visit Teacher Toolkits.