The Physics Classroom » Concept Builders » Forces in 2-Dimensions » Solve It with Fnet = m•a and Vectors » Teacher Notes

Notes:

The Solve It with Fnet = m•a and Vectors 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:

While not all Physics courses delve heavily into combining vectors and Newton's Laws, those who do will appreciate this Concept Builder. This Concept Builder three variations on one physical situation. The physical situation involves the application of a force at an angle to the horizontal in order to accelerate an object across the horizontal surface. In each case, the applied force is directed upward and rightward and the magnitude and angle (with the horizontal) is given. Students must analyze the situation, determining the x- and y-components, the gravity force (mass is stated), the normal force, the friction force (in Master and Wizard Levels), the net force, and the acceleration. They must also identify that quantity associated with the given information. The numerical values provided to students will vary from session to session and from student to student as they are randomly generated. 

This Concept Builder consists of three difficulty levels. Each level includes two situtations that must be analyzed. A free-body diagram and a short description is provided. Three or more numerical values (for example, mass, force value, angle of force with horizontal, and friction information) are provided. Students must identify the values of up to 10 quantities (8 in Apprentice level and 9 in Master level). A few of the values are stated in the provided description. The others must be calculated from an understanding of  the relationships implicit to the situation. It is not necessary to start with the Apprentice Level or to finish with the Wizard Level. The activity was designed such that classrooms jump in and jump out at the locations that are most appropriate to them. We recommend that teachers view the Questions or do the Concept Builder in order to make judgements about what works best for their specific classes.

The three difficulty levels are differentiated as follows:
  • Apprentice Difficulty Level Questions 1-2: Analyze a problem involving a force applied at an angle to the horizontal to cause a horizontal acceleration. No friction.
  • Master DifficultyLevel Questions 3-4: Analyze a problem involving a force applied at an angle to the horizontal to cause a horizontal acceleration. Friction value is given.
  • Wizard Difficulty Level Questions 5-6: Analyze a problem involving a force applied at an angle to the horizontal to cause a horizontal acceleration. Coefficient of friction is given.
In order to complete a difficulty level, a student must successfully analyze both situations of that level. A successful analysis involves determining all the correct information requested - like the x- and y-components of the applied force, the normal force, the net force, and the acceleration. A student can enter values one blank at a time and use the Check Answers button to check; feedback will be immediate and correct response cannot be changed thereafter. Incorrect responses can be corrected until they are correct. There is no penalty for misses or difficulty (other than the extra time and frustration that can be associated with it). When both analyses are correct, the student is returned to the Main Menu and (if logged in as a Task Tracker user), the Trophy for that difficulty level is displayed.

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 situation. Formulas, tips, suggestions, etc. are provided. 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 Solve It! (with Vectors and Fnet=m•a) 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 Forces in Two Dimensions 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 mission F2D2 as an accompaniment 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 Forces in Two Dimensions module can be found on Part 2 of the six-part App series. Visit Minds On Physics the App.
     
 

Additional resources and ideas for incorporating Solve It! (with Vectors and Fnet=m•a) into an instructional unit on Newton's Laws  can be found at the Teacher Toolkits section of The Physics Classroom website.  Visit Teacher Toolkits.