The PhET Projectile Motion simulation from the University of Colorado Boulder lets students fire a cannon, change the launch angle and speed, and measure where the projectile lands, all without cleaning up a single ball. This PhET projectile motion lab turns the simulation into a structured investigation: students predict, test, record data, and compare their results with the range equation.
The lab fits a 50-minute physics period and works in Algebra-based or introductory physics. It pairs well with our other free simulation guides, such as the Energy Skate Park lab and the Gravity and Orbits lab. You can find more options on our classroom simulations page.
In this guide8 sections
Learning goals
- Describe how launch angle affects the horizontal range of a projectile.
- Explain why complementary angles (such as 30° and 60°) give the same range on level ground without air resistance.
- Use the range equation to predict and check a landing point.
- Describe how air resistance changes the path and the best launch angle.
Setup (5 minutes)
- Open the free PhET Projectile Motion simulation in a web browser (it runs in HTML5, so Chromebooks work).
- Choose the first screen. Drag the cannon down so it launches from ground level (height 0 m).
- Make sure air resistance is off for Parts 1 and 2.
- Set the initial speed to 15 m/s.
- Show students the measuring tool, which reads time, range, and height at points along the path.
Part 1: Predict and test launch angles (15 minutes)
Before firing, students write a prediction: “Which angle will send the projectile farthest?” Most students guess something steep or something close to horizontal, which makes the result memorable.
Students then fire the cannon at each angle in the table, keeping the speed at 15 m/s, and record the range. The expected values below come from the range equation R = v² sin(2θ) / g with g = 9.81 m/s², so students’ readings should be very close.
| Launch angle | Predicted range (m) | Measured range (m) | Expected range (m) |
|---|---|---|---|
| 15° | 11.5 | ||
| 30° | 19.9 | ||
| 45° | 22.9 | ||
| 60° | 19.9 | ||
| 75° | 11.5 |
Ask: “What pattern do you see?” Students should notice that 45° gives the greatest range and that pairs of angles adding up to 90° land in the same place. Ask them to compare the flight time and maximum height for 30° and 60°: same range, very different paths.
Part 2: Use the range equation (10 minutes)
Give each group a target distance, for example 18 m. Using R = v² sin(2θ) / g, students calculate an angle that will hit it at 15 m/s, then test it in the simulation using the target. For 18 m, sin(2θ) = 18 × 9.81 / 225 ≈ 0.785, so 2θ ≈ 51.7° and θ ≈ 25.9°. The second solution, about 64.1°, also works, which is a nice check on Part 1.
Extension questions for stronger students:
- At 45° and 15 m/s, how long is the projectile in the air? (t = 2v sin θ / g ≈ 2.16 s)
- What is the maximum height? (h = v² sin²θ / 2g ≈ 5.7 m)
- What happens to the range if the speed doubles? (It becomes four times larger, because range depends on v².)
Part 3: Add air resistance (10 minutes)
Turn air resistance on and choose a light object with a large surface area and a dense, compact one, if your version of the simulation offers different objects. Students repeat the 30°, 45°, and 60° launches and record what changes.
Guide the discussion toward three observations: the range is shorter with air resistance, the path is no longer symmetric (the projectile comes down more steeply than it went up), and the angle that gives the greatest range is now less than 45°. This is why real athletes rarely launch at exactly 45°.
Wrap-up questions (10 minutes)
- Why do 30° and 60° produce the same range without air resistance?
- Which angle gives the longest flight time? Is that the same angle that gives the longest range? Explain.
- Name one real situation where launching below 45° makes sense.
- What is one limitation of using a simulation instead of a real launcher?
For a quick way to collect answers, use one of these questions as an exit ticket, and if you are building a full physics unit, the PhET Circuit Construction Kit lab follows the same predict-test-explain structure.
Frequently asked questions
Is the PhET Projectile Motion simulation free?
Yes. PhET simulations are free to use and run in a web browser, including on Chromebooks and tablets.
What grade level is this lab for?
The angle and range parts work for grades 8–12. The equation and air resistance parts fit high school physics, including algebra-based courses.
Why don’t my students’ results match the equation exactly?
Check that the cannon is at ground level, air resistance is off, and students read the range where the projectile lands. Small differences come from rounding and from where the measuring tool is placed.
Can students do this lab at home?
Yes. Because it runs in a browser, it works as a homework or sub-day assignment. Students only need the data table and questions.
Final thoughts
Projectile motion can feel like a page of equations until students see a cannonball land exactly where they predicted. This PhET lab gives them that moment, then complicates it with air resistance so they learn when a model works and when it doesn’t. Pair it with the Build a Molecule lab or the States of Matter lab for more simulation days across your science courses.
