Lab Motion and Error

Procedure

Please note: the motion sensors we are using in lab today are pretty sensitive, so be patient with them; in some cases we might have to fiddle around with them to get them to read what you want them to read.

You have three tasks for this lab.  In all the cases, you are trying to reproduce motion (physically) which is described to you.

Setup:

Obtain a sonic ranger (motion detector), and plug it into a digital input of the LabQuest interface, which you need to attach to your PC.  The motion detector can simply be placed on a table.  You need to face the detector in a direction which has a minimum number of obstacles and at least 2 meters range.

filler image filler image gd051399.gif (4780 bytes)

The minimum range that the motion detector can measure is 0.5 m, so you will always want to be at least that far away.  The maximum range is supposed to be 6 m, but is not the case with all of them.  Lets figure out the range of the meter:

  1. Start LoggerPro on the computer that the LabQuest is attached to.
  2. If it does not recognize the motion detector click Experiment, connect, and choose "com 1".
  3. If it still cannot find the equipment, make sure all of the cables are plugged firmly into the interface, and repeat Step 2.
  4. Click the setup button filler image.  Choose the "collection" tab, and change experiment length to 30 seconds (or anything you want that is long enough to do the experiment).  "OK" your way out of the setup screen.  
  5. Have someone stand in front of the motion sensor and click the Collect button (to the right of your setup button).  If you do not have a Collect button, then please ask the instructor.
  6. The person in front of the sensor should walk toward and away from the sensor until they reach the minimum and maximum distances.  (When you reach the minimum and maximum distances, it will no longer detect that you are moving closer or farther away.)

Procedure:

Because of restrictions of the room, you probably want to stay between 0.5 and 1.5 meters from the sensor for the experiments.

  1. First, lets try to move at a constant velocity.  Your goal is to move at a constant speed of 0.50+/-0.05 m/s, toward or away from the sensor (for about 1m, or more if you like).  Practice as much as you like, and when you think you have gotten pretty close, you will save the data:
    1. To save the data, you need to copy the position vs time data to Excel for analysis (we will ignore all the other data).
  2. The analysis of this data will be described in the Analysis section of the lab.
  3. Try to reproduce this position vs. time graph qualitatively:

    filler image

    Simply print the best try and tape it into your lab notebook.
  4. This challenge is quantitative. Try to reproduce the velocity vs. time graph shown below. Save your DATA (in Excel or LoggerPro or as a text file) and email it to your lab instructor, and we will determine quantitatively who is closest to the original, and the best reproduction will win a prize!



    Also print the graph with your best try and tape it into your lab notebook.
  5. Please be sure to put away your motion detector and clean up around your lab station.

Department of Physics

Randolph College