Physics students are intrinsically motivated by the topic of skydiving. When they begin the source they know that it has something wot do with Physics; they are just not sure what. And so when the topic comes up their interest is piqued. And the fact that it provides such a great application of Newton's laws makes its inclusion in the first year Physics course a must. There are several troublesome ideas that arise out of such discussions and sometimes it is the topic of skydiving that helps students overcome a long-held misconception. For instance, consider the following:

• Students commonly mistaken velocity and acceleration. A skydiver is increasing its velocity but decreasing its acceleration. The confusion of the two quantities must be resolved to truly understand the nature of a skydive.
• Many students believe that an object cannot be moving if the forces acting upon it are balanced. The concept of terminal velocity often times helps students to understand that a balance of forces does not stop an object from moving; it just stops them from accelerating.

The Air Resistance and Skydiving Concept Builder leads a student systematically from an understanding of air resistance to a comprehension of its role in skydiving, particular in how it influences the velocity, acceleration, and net force over the course of time. The Concept Builder is comprised of 12 Question Groups spread across three different activities. Each activity engages students in a slightly different task. The three activities are described as follows:
 

• Air Resistance: Question Groups 1-4 Identify the manner in which air density, object speed, and object cross-sectional area affect the air resistance force.
• Vector Diagrams: Question Groups 5-8 Identify the set of vector diagrams that show how the velocity, acceleration, air resistance force, and net force change over the course of a skydiver's fall.
• Velocity-Time Graph: Question Groups 9-12 Match free-body diagrams and information about the relative acceleration, net force, and air resistance to locations on a velocity-time graph representing a skydiver's motion.

Questions in the same question group are very similar. The Concept Builder is coded to select a question at random from among those in the group. That question is delivered to students. If they miss the question, they will eventually have to answer two questions correctly within the same Question Group. This approach provides the student extra practice on situations for which they exhibited difficulty.

As a student progresses through an activity, a system of stars and other indicators are used to indicate progress on the activity. A star is an indicator of correctly analyzing the situation (or Question Group). 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 activities.

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 Air Resistance and Skydiving Concept Builder. These include:
 

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