The following guide pertains to setting up Vernier (BTD) Photogates for data collection in a projectile motion experiment.
Photogate (VPG-BTD)

If you are looking for instructions for setting up a Go Direct Photogate, see
How do I set up Go Direct Photogate for data collection in a projectile motion experiment?

If you would like general photogate set up help, see
How do I set up Vernier Photogates (VPG-BTD) for data collection with Logger Pro 3?
How do I set up Vernier Photogates (VPG-BTD) for data collection using LabQuest App?
How do I set up Vernier Photogates (VPG-BTD) for data collection using Graphical Analysis 4?

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. Set up the photogates or projectile launcher as instructed and open the corresponding experiment file, either “08A Projectile Motion.cmbl” or “08B Projectile Motion.cmbl”, from the Experiments/_Physics with Vernier folder in Logger Pro.

Writing Your Own Experiment?
If you are writing your own projectile motion experiment, you will need to set the photogate mode and enter the correct distance/length to get meaningful data. Below is an outline for some common data-collection set ups both when using Logger Pro and a LabQuest to operate the photogates.

  • If you plan on using a computer and Logger Pro to run the experiment, you will need to open the file listed. If you plan on using a LabQuest to run the experiment, you will need to select the correct photogate mode in data-collection parameters.
  • If you plan to use the Vernier Projectile Launcher (VPL) or the Time of Flight Pad (TOF-VPL), you may need to adjust the default settings in Logger Pro or LabQuest App to measure and record the data you have in mind.
Desired Measurement and Physical Set Up Logger Pro Experiment File (and Folder) OR LabQuest App Photogate Mode Appropriate Distance or Length Further Details
Launch velocity from a horizontal table top Pulse Timer – Two Gates.cmbl
(Found in the Experiments/Probes & Sensors/Photogate folder)
OR
Pulse Mode in LabQuest App
OR
Speed through gate-Use gate separation on Graphical Analysis 4
Distance between photogates Set up two photogates so that the projectile will pass through both of them just before leaving the table top. Measure the distance between the gates. Test data collection by pressing Collect and placing a finger in the first photogate and then the second. Check the data table to verify that the events were recorded and that the velocity was calculated correctly.

Timing starts when the object breaks the beam of the first photogate and ends when it breaks the beam of the second photogate. The launch speed of the object is determined by dividing the distance between the photogates by the measured time.

Launch velocity from an angled track One Gate Timer.cmbl
(Found in the Experiments/Probes & Sensors/Photogate folder)
OR
Gate Mode in LabQuest App
OR
Speed through Gate-Use object/flag width on Graphical Analysis 4
Length of projectile passing through photogate

Note: If the length entered differs from the actual length of the projectile that passes through the beam, the launch speed measurement will be off. For example, if you rolled a marble through the gate, you would need to know the diameter or secant of the ball that went through the beam.

Measure the length of the projectile that will pass through photogate. Set up a single photogate near the end of the angled track so that the projectile moves through it just before launch. Test data collection by pressing Collect and swiping a finger through the photogate. Check the data table to verify that the events were recorded and that the velocity was calculated correctly.

When the projectile passes through the photogate, it measures how long the beam is blocked. The object’s speed (at the position of the photogate) is determined by dividing the length of the object by the blocked time.

Launch velocity from a projectile launcher Projectile Launcher.cmbl
(Found in the Experiments/Probes & Sensors/Projectile Launcher folder)
OR
Pulse Mode on original LabQuest
OR
Projectile Launcher Mode in LabQuest App (v2.8.4 or newer) and Graphical Analysis 4

Note: If you are using Graphical Analysis 4 or  LabQuest App version 1.6 or newer, the Projectile Launcher will automatically be identified when you plug it into the LabQuest.

By default, the length will be set to 5 cm, the distance between the two photogates built into the Projectile Launcher. Be sure to set up the Projectile Launcher on a horizontal surface. Test data collection by pressing Collect, placing a finger across the aluminum barrel of the Launcher, and then removing it, generating an event pair. Place and remove your finger a second time to generate a second pair. Check the data table to verify that the events were recorded and that the velocity was calculated correctly.

Timing starts as soon as the projectile is launched. As it passes through the barrel, it passes through two built-in photogates, separated 5 cm from each other. Timing starts when it passes through the first, and ends when it passes through the second. The launch speed is calculated by dividing the 5 cm photogate separation by the elapsed time.

Time of flight from a horizontal table top with Vernier Time of Flight Pad Pulse Timer – Two Gates.cmbl
(Found in the Experiments/Probes & Sensors/Photogate folder)
OR
Pulse Mode in LabQuest App, set to end data collection after 4 events
OR
Speed through gate-Use gate separation on Graphical Analysis 4
Not necessary if you are only looking for time of flight

By default, the distance is set to 5 cm. The LabQuest/Logger Pro will calculate a speed based on this distance. For time of flight measurements, disregard this speed.

Set up a single photogate at the end of the horizontal table top at a point just before it leaves the end. Daisy-chain the Time of Flight Pad into the photogate. Test data collection by pressing Collect and swiping a finger through the first photogate. Then, press the Time of Flight Pad firmly. Check the data table to verify that the events were recorded and that the recorded time is correct.

When the projectile passes through the first photogate, 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 Time of Flight.cmbl
(Found in the Experiments/Probes & Sensors/Projectile Launcher folder)
OR
Pulse Mode on original LabQuest, set to end data collection after 6 events
OR
Projectile Launcher mode on Graphical Analysis 4 or LabQuest App (v2.8.4 or newer), with Time of Flight Pad option selected
Not necessary if you are only looking for time of flight When using the Pad, the data-collection mode must be changed to stop collection after six events. After connecting the Launcher to the LabQuest,
1) Tap the Mode field to enter the Data Collection setup dialog. Set data collection to end after six events, and tap OK.
2) Test data collection by tapping Collect, and place a finger across the aluminum barrel of the Launcher, and remove your finger, generating an event pair. Place and remove your finger a second time to generate a second pair. Then press a finger firmly on the Pad and release. This will generate a third pair of events.
3) Display the data table to see the times corresponding to the six events.

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

  • The user manuals for the Vernier Projectile Launcher (VPL), Go Direct® Projectile Launcher (GDX-PL), and Time of Flight Pad (TOF-VPL) contain helpful usage tips and guidelines.
  • Graphical Analysis 4 and LabQuest App (v2.8.4 or newer) includes a Photogate timing mode – Projectile Launcher.
    • This is the default timing mode when using the Vernier Projectile Launcher or the Go Direct Projectile Launcher.
    • You can use two Vernier BTD photogates and optional Time of Flight Pad with the Projectile Launcher timing mode as long as the photogates and Time of Flight Pad are all daisy-chained together.
    • You cannot use Go Direct Photogates with the Projectile Launcher timing mode.
  • The Probes & Sensors/Projectile Launcher folder includes an additional experiment file, in addition to the Projectile Launcher.cmbl and Time of Flight.cmbl files mentioned above:
    • Angle Range.cmbl – This experiment file provides a template for an exploration of how the horizontal range of a projectile changes with launch angle.
    • Projectile Launcher.cmbl – This experiment file is a generic template for experiments using the Projectile Launcher and is set up to measure and record launch velocity.
    • Time of Flight.cmbl – Like Projectile Launcher.cmbl, this experiment file is set up for the Projectile Launcher when it is used with the Time of Flight accessory.