### Notes:

The Normal Force Card Sort 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 Concept Builder 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:

The Normal Force Card Sort Concept Builder is based on a card-sorting idea that has become popular in the Physics teaching community. In a card sort activity, students are given a collection of cards representing several physical scenarios. The students then sort the cards into categories that have a unique set of criteria. This Concept Builder is the interactive and digital version of that idea. Students are presented with a set of physical situations and must sort them into one of four categories based upon the strength of the normal force or scale reading. Categories include: A. Normal Force = Weight of Object; B. Normal Force > Weight of Object; C: Normal Force < Weight of Object; and D: Not enough information provied to decide.

This particular Card Sort 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 Card Sorting 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.

There is a good deal of randomization in this Concept Builder. The ordering of the cards is randomized and the number assigned to each card is also randomized. This reduces the likellihood that one student or group of students copies off another. And the fact that a student never knows which of their sorts is correct and which is incorrect also reduces the copying effect. The strategy also encourages some rich discussion among students and groups of students as they debate over their personal choices and make efforts to defend their decisions.

The organization of the Concept Builder as described above leaves a lot of freedom for teachers to decide upon how to use it. First, teachers can choose which of the three difficulty levels are must suited to their students. We recommend previewing the activity (or viewing the Questions in the separate file) in order to judge which levels would be most appropriate for their students. Teachers may want to provide students with a couple of options to accomodate both those who find Physics more difficult and those who are confident students.

Teachers can also decide whether this Concept Builder works best as a group activity with 2-3 students per screen or whether it works best as an individual check-up. While we intend most of our Concept Builders to be used in the classroom with one student per screen, we tend to prefer this one as a grouped activity.

Finally, teachers can decide as to how they use the Health Rating. We recommend that it not be used in a punitive manner. Concept Builders can be difficult enough tasks without the fear of being slapped with a low grade once it has been completed. Our recommended strategy is to require that students complete a difficulty level with a health rating below a minimum specified level; if they do not then they must redo it until they have surpased he required minimum health rating. The second pass through should be much easier and a great way to seal up the learning that occurred on the first pass through.

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.

### Related Resources

There are numerous resources at The Physics Classroom website that serve as very complementary supports for the Normal Force Card Sort 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 NL4 and NL5 of the Newton's Laws module provide great complements to this Concept Builder. They are best used in the middle to later stages of the learning cycle. 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 ...

Recognizing Forces
Drawing Free-Body Diagrams

Visit the Curriculum Corner - Newton's Laws.

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