You may want to use a photogate (either Go Direct® Photogate (GDX-VPG) or Photogate (VPG-BTD)) to measure angular velocity of the Go Direct® Centripetal Force Apparatus (GDX-CFA) to help students gain insight into rotational motion. You can set up the photogate to have the beam pass through the arm of the photogate with the assistance of a ring stand and right-angle clamp.

You can accomplish this with Graphical Analysis software by connecting your photogate and Go Direct® Force and Acceleration Sensor (GDX-FOR). In the data collection settings select Photogate Timing and then Angular Motion. Change the Number of spokes to 2, and check radians for units. You will need to manually start and stop data collection.

If you are using a LabQuest App for data collection (LabQuest 2 or LabQuest 3 only), connect your force sensor first so the data collection mode is Time Based. When setting up the data collection using the Photogate (VPG-BTD), the primary mode will be Time Based. Leave this as is and click on the Photogate Mode (below in the dialog box) and select Pulse. The distance can be set to 3.14 radians for a direct determination of angular velocity.

The Go Direct® Photogate (GDX-VPG) will default to measuring velocity. To convert this to angular velocity, create a calculated column that divides the velocity data by the radius. In this case the radius will be the distance from the photogate eyes to the center of rotation. This distance can be read from the scale on the beam. Use care in setting the photogate square with the beam so that the distance between the two photogate eyes is consistent with the software.

Go Direct Centripetal Force Apparatus, Troubleshooting and FAQs