### Notes:

The Match That Free-Body Diagram Concept Builder is an adjustable-size file that displays nicely on smart phones, on tablets such as the iPad, on Chromebooks, and on laptops and desktops. The size of the Interactive can be scaled to fit the device that it is displayed on. The compatibility with smart phones, iPads, other tablets, and Chromebooks make it a perfect tool for use in a 1:1 classroom.

### Teaching Ideas and Suggestions:

For most Physics classes, a primary goal is to be able to use Newton's second law to analyze a physical situation and determine the acceleration or the value of an individual force acting upon an object. The precursor to accomplishing such a goal is the ability to identify the forces acting upon an object and to represent those forces by a free-body diagram. The free-body diagram represents the individual forces by a vector arrow pointing in the direction of the force. The relative length of such arrows reflects the strength of the force; a stronger force is represented by a longer arrow and a weaker force is represented by a shorter arrow. The forces are typically labeled to indicate the type of force - for instance, Fgrav, Fnorm, Ftens, Ffrict, etc. This Concept Builder is designed to assist students in strengthening their skill at recognizing the forces that are present in a given situation and identifying the free-body diagram consistent with the situation. We think it is a natural follow-up to our Recognizing Forces Concept Builder. We also think that a natural follow-up to this activity is our Drawing Free-Body Diagrams Interactive in our Physics Interactives section.

This Concept Builder is intended for use in the early to middle stages of a learning cycle on Newton's Second Law. It makes for an exceptional formative assessment of student understanding of student ability to identify a free-body diagram that is consistent with a given situation. Students are given a short description of a physical situation and must pick a free-body diagram from a selection of five choices that is consistent with the situation.

This Concept Builder was intended as an in-class activity. The Concept Builder includes 12 different situations, organized into two different ability levels. 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 two levels is as follows:

• Master Level (moderate difficulty): Includes six situations in all.
• Wizard Level (most difficult): Includes 12 situations - the six from the Master Level plus six additional situations. We do not feel that the situations of the Wizard level are any more difficult than in the Master Level; it's just that there are more of them.

In order to complete a level, a student must successfully analyze each situation. If a student's analysis is incorrect, then the student will have to correctly analyze the same situation twice in order to successfully complete the level. This approach provides the student extra practice on situations for which they exhibited difficulty. Each time a new question is presented for a troublesome situtation, the answer options are scrambled.

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 situation. Once a star is earned, that situation is removed from the que of situations 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 situation and will have to correctly analyze it twice before earning a star. A yellow box is an indicator that the situation must be correctly analyzed one time in order to earn a star. Once every situation at a level has been analyzed, the student earns a trophy that 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-building activity is the Help Me! feature. Each situation is accompanied by a Help page that discusses in detail 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.

### Related Resources

There are numerous resources at The Physics Classroom website that serve as very complementary supports for the Match That Free-Body Diagram Concept Builder. These include:
• Minds On Physics Internet Modules:
The Minds On Physics Internet Modules include a collection of interactive questioning modules that help learners assess their understanding of physics concepts and solidify those understandings by answering questions that require higher-order thinking. Assignments from the Newton's Laws module make for a great complement to this Concept Builder. They are best used in the middle to later stages of the learning cycle. We recommend assignments NL4, NL5, NL6, and NL9 as accompaniments to this activity. Visit the Minds On Physics Internet Modules.

Users may find that the App version of Minds On Physics works best on their devices. The App Version can be found at the Minds On Physics the App section of our website. The Newton's Laws module can be found on Part 2 of the six-part App series. Visit Minds On Physics the App.

• Curriculum/Practice: Several Concept Development worksheets at the Curriculum Corner will be very useful in assisting students in cultivating their understanding, most notably ...

Balanced vs. Unbalanced Forces
Net Force Help Sheet
Recognizing Forces
Free-Body Diagrams
Drawing Free-Body Diagrams

Visit the Curriculum Corner - Newton's Laws.

• Physics Interactives: There is an activity in our Physics Interactives section that is an excellent accompaniment to this activty. It is titledDrawing Free Body Diagrams and it would make an excellent follow-up to this activity.

Visit the Drawing Free Body Diagrams Interactive.

Additional resources and ideas for incorporating Match That Free-Body Diagram into an instructional unit on Newton's Laws  can be found at the Teacher Toolkits section of The Physics Classroom website.  Visit Teacher Toolkits.