Notes

While not all Physics courses spend time on inclined planes, those that do know that the task of drawing free-body diagrams for incline planes can be difficult. The role of this Concept Builder is to give students practice drawing free-body diagrams. The Concept Builder involves 8 different situations that must be analyzed. Our simplest situations are objects moving upward or downward along the inclined plane with or without friction. Our most complex situations involve the additional force of a rope or person pushing or pulling the box up the inclined plane with or without friction. The Apprentice Difficulty Level includes the four simplest situations. The Master Difficulty Level includes the four most complex situations. The Wizard Difficulty Level includes all eight situations and is equivalent to doing both the Apprentice and the Master Levels combined.

The Concept Builders requires that students identify the direction of all forces and give them labels. The Concept Builder gives no attention to the relative length of the forces and no information about the direction of acceleration for any of the situations. Thus, all arrows are the same length ... which might feel awkward at times. A second Concept Builder will be out soon that puts greater attention on the relative length of the forces and of gravity's components. Each situation or Question Group consists of four questions which are chosent at random. The individual questions in the foursome vary in terms of the angle of the incline and whether it is a right-facing or a left-facing inclined plane. This requires that students be very principled as they decide upon force directions (e.g., using the principle that the normal force is perpendicular to the incline) and not just operating by memory (for example, the normal force is always directed upwards and rightwards).

This Concept Builder is intended for use in the early stages of a learning cycle on inclined planes. In fact, it can be completed before a discussion of force components and problem-solving. This Concept Builder works well as both an in-class activity and (with Task Tracker) as a homework assigment. 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 difficulty levels is as follows:
 

• Apprentice Difficulty Level Question Groups 1-4: Includes our most basic situations of a box moving up or down and inclined plane with or without friction.
• Master DifficultyLevel Question Groups 5-8: Includes our most complex situations in which a box is pulled up an inclined plane by a rope or a person with or without friction.
• Wizard Difficulty Level Question Groups 1-8: Includes all questions from the Apprenticeand Master Difficulty Levels.

 

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.

There are numerous resources at The Physics Classroom website that serve as very complementary supports for the Free-Body Diagrams for Inclined Planes Concept Builder. These include:

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