Using Video to Enhance the Observation of Motion and Forces Demonstrations

2010 CSTA Conference

Darren Fix

Spring View Middle School

Part 1 Introduction  

There are basically 3 components in teaching motion to students.  

  1. Force
  2. Position
  3. Time

Demonstrations are a helpful tool in showing these components.  Unfortunately there are a few drawbacks that hinder in student comprehension.

  1. Not all students can see.  With 36 plus students in a class, most are going to have a terrible viewing angle of the demonstration.
  2. The demonstration itself is too fast.  Students can’t easily identify the forces involved and how the position of the object changed over time.

What can a teacher do, to address these issues? A teacher can do the following:

  1. Make the demonstration viewable to all students.
  2. Capture video of the demo.
  3. Break it down in slow motion.
  4. Annotate it.

Here is a very simple example of a centripetal force demonstration (quicktime or YouTube).  

Part 2 How Do I Do It?

A teacher can make a demonstration viewable to all students by utilizing a

  1. Webcam.  A simple web cam can be used that costs between $20 and $50.  HD webcams might not be practical for older computers.  You can hold the webcam in different positions by using a simple ring stand and test tube clamp.  
  2. Video projector.  A must so that all students can see. The brighter the projector the better.

A teacher can then capture video of the demonstration by using a

  1. Webcam.  While the students are watching the demonstration, a teacher can record the demo.  This doesn’t require the teacher to spend much extra time.  The drawback include poor lighting and not the best take.
  2. Cell Phone Camera.  The most recent iPhone shoots impressive HD video.  The benefit is always having a camera around and not spending extra money.  The drawback is it’s not easy keeping the camera steady (no easy tri-pod solution).
  3. HD Camera.  These cameras shoot excellent video.  There are a wide range of HD cameras.  Cheap Flip cameras ($199) to mid level consumer cameras (Samsung s10 $649) to high end prosumer cameras provide a huge selection.  Ideally a camera that can shoot hi frame rates (slow motion) would be the best, but it’s definitely more expensive.

With any camera a teacher can shoot good video by considering a couple of factors:

  1. Simple Backgrounds.  You want the viewer to focus only on the motion, not anything in the background.  Pick a color background the contrasts with the object.  If the object is white, pick a dark background.  If the object is dark, use a bright background.  Simple backgrounds also reduce the amount of blocking (video compression) that happens during rendering of the video. Simple backgrounds can be made of butcher paper or cloth.
  2. Lighting.  Make sure the objects are well lit.  Some classrooms have excellent lighting while others do not.  Cheap lamp clamps ($10) can be used.

Now that you have captured the video, you can either use the raw video right away or you can edit it.  

  1. Editing.  Editing the video allows you to only show the action parts and not the stuff in between.  Any editing software will do, but you don’t need any high end stuff.  iMovie ($99 for iLife) for the Mac is a great tool and I like Vega Movie Studio ($49 education pricing) for Windows.  Try trial versions if available and use what is easiest for you.  Decrease the playback rate (slow motion) for key sections of the motion.  This allow students to more easily see what is going on.  
  2. Rendering.  This can get tricky.  I like rendering it in 720 format in Quicktime Files. The reason why I like Quicktime is due to the ability of advancing the playback of the video one frame at a time both backwards and forwards.  Other video players and file types can’t do that.

Now that you have the video of the demonstration, you can show it to your students in repeated viewings and in slow motion.  It helps students to precisely see what you want them to notice such as force and direction.  Just like the color analyst of a sporting event uses a telestrator to get his/her point across to the viewing audience, the teacher can do the same thing for the students. Teachers can use annotation software.  

  1. Annotation Software.  I use ZoomIt for Windows.  It’s free and simple to use.  Just pause the video that you are showing and then use the software to draw force vectors and direction arrows.  The software is activated by using certain keyboard combinations.
  2. Drawing Table.  A mouse is really hard to control for drawing precisely positioned lines.  A tablet makes is much easier.  I use a Hanvon graphic 5 x 4 tablet ($59.99 for Win and Mac).  There is a bit of a learning curve, but it will be worth it.  

Part 3 Examples of Motion and Forces Demos

Show the following demos of inertia:

  1. Chalk ring (download quicktime or view on YouTube)
  2. Beaker books (download quicktime or view on YouTube)
  3. Eggs (download quicktime or view on YouTube)
  4. Mass effect on Inertia (download quicktime or view on YouTube)
  5. Apple/knife (download quicktime or view on YouTube).
  6. Adding forces ball demo (download quicktime or view on Youtube)
  7. Friction force and motion (download quicktime or view on YouTube)

Part 4 Recording an Annotated Video

A good way to save all the annotations and your narrations is to used screen capture software.  This video then can be viewed by your absent students.  The best software to do this is Camtasia Studio ($179 education price for Mac and PC).