The following guide pertains to setting up a Go Direct Photogate for data collection in a projectile motion experiment.
Go Direct® Photogate (GDX-VPG)

If you are looking for instructions for setting up a Vernier (BTD) Photogate, see
How do I set up Vernier Photogates (VPG-BTD) for data collection in a projectile motion experiment?

If you would like general photogate set up help, see
How do I set up a Go Direct Photogate to collect data using LabQuest App?
How do I set up a Go Direct Photogate to collect data using Graphical Analysis or Graphical Analysis Pro?
How do I set up wired Vernier Photogates (VPG-BTD) for data collection using Graphical Analysis and Graphical Analysis Pro?

Although the photogate output is quite simple (blocked or unblocked), when the timing starts and stops is determined by the photogate timing mode in the software. There are different modes for different types of experiments. Which mode you should choose depends on what quantity you want to measure.

Doing a Vernier Experiment?
If you are doing the projectile motion experiment from Physics with Vernier, instructions for how to set up the photogates are in the student experiment files, for both the table top and projectile launcher versions.

Writing Your Own Experiment?
If you are writing your own projectile motion experiment, you will need to set the photogate mode to get meaningful data. Below is an outline for some common data-collection set ups both when using Graphical Analysis 4 and LabQuest App to operate the photogates.

Desired Measurement and Physical Set Up Go Direct Photogate Sensor Channel Data Collection Mode Further Details
Launch velocity from a horizontal table top Object Velocity
(this is the default sensor channel)		 Time Based Set up the photogate so that the projectile will pass through it just before leaving the table top.

Timing starts when the object breaks the beam of the first internal gate and ends when it breaks the beam of the second. The launch speed of the object is determined by dividing the internal gate separation (2.0 cm) by the measured time.
Launch velocity from an angled track Object Velocity
(this is the default sensor channel)		 Time Based Set up the photogate so that the projectile will pass through it just before leaving the table top.

Timing starts when the object breaks the beam of the first internal gate and ends when it breaks the beam of the second. The launch speed of the object is determined by dividing the internal gate separation (2.0 cm) by the measured time.
Launch velocity from Vernier Projectile Launcher N/A Photogate Timing – Projectile Launcher

This it the default data collection mode for a Projectile Launcher in Graphical Analysis 4 and LabQuest App (v2.8.4 or newer)

 Be sure to set up the Projectile Launcher on a horizontal surface. Timing starts as soon as the projectile is launched and ends when it passes through the second embedded photogate. The launch speed is calculated by dividing the 5 cm photogate separation by the elapsed time.

You can set the Projectile Launcher mode to use the ball diameter and time the first gate is blocked to measure the launch speed if desired.
Time of flight from a horizontal table top with Vernier Time of Flight Pad Object Velocity and Gate 1/Remote Gate-Timing Time Based Set up the Go Direct Photogate at the end of the horizontal table top at a point just before it leaves the end. Be sure that the projectile will pass through internal Gate 1 before Gate 2. You will need a special cable (Go Direct® Time of Flight Pad Cable (TOF-CB-GDX), sold separately) to daisy-chain the Time of Flight Pad into the photogate.

When the projectile passes through internal Gate 1, timing begins. When the projectile strikes the Time of Flight Pad, timing stops.
Time of flight from a projectile launcher with Vernier Time of Flight Pad N/A Photogate Timing – Projectile Launcher with Time of Flight Pad option selected The time of flight calculated by the software is the total time from when the first photogate was blocked to the time when the Time of Flight Pad registers an impact.

Further Information

Published: December 30, 2018. Updated: August 8, 2020.