You will be describing motion several ways: written description, motion maps (strobe photographs), and graphical representation. You should be familiar with the techniques of presentation except possibly motion maps, which are described below.
Motion Maps
Motion Maps can be thought of as a strobe photograph. A strobe photograph has many images on one picture. Each image represents a certain moment in time. In addition, there is a set time interval between each image. (A similar pattern could be made by cutting out the frames of a movie and laying them on top of each other). For example, a ball rolling uniformly with the strobe time interval set to 1.00 seconds may look like this:
Besides the time between snapshots, it is often good to tell where the object was at the first strobe (and sometimes the last). Note, the value of the time step can be different for different motion maps. Make sure the time step size, which is your choice, is small enough to make the motion clear. The maps can also include arrows to represent direction and magnitude (arrow length) of the velocity and acceleration.
When the motion "back tracks", the map drawings are shifted to make all the pictures clear.
Experimenting with Motion
Use the sonic range finder with with either a calculator and CBL or a calculator and LabPro or a ULI.
(Notes about the range finder: The range finder emits an inaudible sound and looks for the first reflection of that sound to determine how far away the object is. The system will flash as well as audibly click as a signal it is collecting data. Objects closer than approximately 0.4 m may not register properly because the time interval is too short for the electrical circuits of the range finder. The time is determined by the first reflection detected. Wobbling or swinging your arms will cause noise in your data and you may find a shuffle step while holding your arms still the best way to walk. The sound also goes out in a cone shape and may pick up "side" objects like tables or chairs. The range finder defines its front face as 0.0 m and positive readings going away from it.)
Set the system to collect data in the time graph mode for 10 seconds. Set the y axis minimum at 0.0 m and the maximum at 5.0 m.
Collect data standing approximately 3.0 m in front of the range finder.
How would the graph change if you were to stand 2.0 m away? 4.0 m?
Confirm your prediction by standing at those two positions.
Collect data walking away from the range finder at a steady pace.
What would happen to the graph if you were to walk faster? Slower?
Confirm your predictions experimentally.
What would happen to the graph if you start at 5.0 m and walk toward the range finder?
Confirm your predictions experimentally.
AND/OR
Run the distance matching program (this is a separate program for the LabPro).
Choose distance match.
Have someone walk to match the pattern.
Repeat this and try other patterns.
Choose the velocity match.
Walk to match these patterns.
Answer the following questions about motion in your groups.
Make a strobe picture of a cat walking at a uniform rate for 10 s, with 2 second time intervals.
Make a strobe photograph of a car starting from rest and going to 60 MPH, including 3 strobe pictures after it has reached 60 MPH.
Make a strobe photograph of a plane landing. Include three shots of the plane in the air and continue until the plane is at rest.
Make a strobe of a bike moving at constant velocity to the left.
Make a strobe of a bike accelerating to the right from rest.
What do velocity and speed mean? Do any strobe photographs above relate to them?
What does acceleration mean? Do any strobe photographs above relate to them?
Do the terms "position", "location", "displacement", "distance", "velocity", "speed", or "acceleration" explain why the motion is occurring?