Vernier Motion Probes & Graphing Motion (Marissa Staller)


Marissa Staller


Motion can be graphed in position vs. time and velocity vs. time. Motion graphs help students visualize and interpret motion.


Grade 8 Physical Science


1. The velocity of an object is the rate of change of its position. As a basis for understanding this concept: 

a. Students know position is defined in relation to some choice of a reference point and a set of reference directions

f. Students know how to interpret graphs of position versus time and graphs of speed versus time for motion in a single direction.

Materials needed

Logger Pro (computer software to be used with motion detectors)

Logger Pro Requirements To use Logger Pro, you must have the following equipment:

Windows® 98 SE, Me, 2000, or XP with Pentium® processor, 200 MHz or better, 32 MB available RAM, 60 MB of hard disk space for a minimum installation. Available USB or serial port.

Macintosh OS® 9.2 or OS X 10.2, 10.3 or 10.4, built-in USB port

Vernier motion detector (one needed for class demonstration, or one for each group of students)


            Initial Setup

            Note: The following setup instructions are for the LabPro interface. 

            Before launching Logger Pro, you should:

  • Power the LabPro using the AC power supply or AA batteries.

  • Connect a sensor to LabPro.

  • Connect the USB or serial cable to LabPro.

  • Attach the other end of the interface cable to any unused serial port or USB port on your computer.

    Start up Logger Pro Locate the Logger Pro icon and double-click on it. Mac OS X users can find the icon in the Logger 

    Pro folder created during installation.

    Using the Motion Detector

    Place the Motion Detector on your desk or table (there is a clamp that is available) with the gold disk pointing toward the moving object. Be sure that there is nothing obstructing the Motion Detector from the moving object.

    In Logger Pro, click the Collect button. You should hear a clicking sound from the motion detector. 

    Observe the graph that is being drawn. Data collection will run for 10 seconds.

    There are also files on Logger Pro that can be used so students can match their motion to the graphs. (see picture A)

    Position (m), Velocity (m/s), and Acceleration (m/s2) can all be graphed at the same time, using file 33c. (see picture B)

    Videos can also be used using this software to graph motion. Tutorials are available with the Logger Pro software.


The Motion Detector is used to measure the distance from itself to a target object. It emits ultrasonic pulses and detects the echo from the target. The Motion Detector measures to about 6 meters. Objects can be as close as 15 cm to the green or black detectors; blue detectors have a 50 cm minimum distance.


  1. What does a flat line on a position vs. time graph indicate? 
  2.  What is indicated by negative slope on a position vs. time graph?
  3. What does constant speed look like on a velocity vs. time graph?

A1. A flat line indicates a stationary object.
A2. A negative slope on a position vs. time graph indicates that the object is moving towards the reference point.
A3. On a velocity vs. time graph, constant speed is a flat line. 

Everyday examples of the principles illustrated

Position, velocity, and acceleration can be shown on these motion graphs. Students can use the Motion Detectors to graph position versus time and velocity vs. time for stationary objects, constant speed, and changes in velocity (acceleration).


Motion Graphs