Science Olympiad Trajectory Event Guide: Physics, Device Design, and Scoring
A deep-dive guide to the SciOly Trajectory event — how projectile physics works, how to design and calibrate your device, and what separates good scores from great ones.
Trajectory is one of Science Olympiad's most consistently popular build events. Teams construct a device that launches a projectile — typically a golf ball or tennis ball — at a target at a specified distance, which is revealed on the day of competition.
Because the target distance is unknown until competition day, Trajectory rewards calibration and prediction over raw power. Your device does not need to launch perfectly every time — it needs to be consistent enough that you can calculate how to hit any target distance within the event's range.
The physics: what you actually need to understand
Trajectory is grounded in projectile motion — one of the clearest applications of kinematics in high school physics.
A projectile launched at angle θ with initial velocity v₀:
- Horizontal range:
R = (v₀² × sin(2θ)) / g - Time of flight:
T = (2 × v₀ × sin(θ)) / g - Maximum height:
H = (v₀² × sin²(θ)) / (2g)
For Trajectory, you are typically solving for R given a device with fixed launch parameters, or adjusting angle to hit a known R.
What this means for your device design:
- Changing angle changes range (at 45°, range is maximized; lower angles reduce range, higher angles also reduce range)
- Changing launch force changes v₀, which changes range quadratically — small force changes have outsized effects at distance
- Air resistance matters more than most teams expect at lower velocities — your theoretical calculations will diverge from real measurements if you ignore drag
Device types that work
The most common Trajectory devices use one of three mechanisms:
Elastic (bungee/surgical tubing): Consistent force, easy to adjust tension, relatively compact. Sensitive to tubing wear over the season — keep spares and track tubing age.
Gravity (pendulum/counterweight): Very consistent if built rigidly. Harder to adjust for different distances (you change the angle rather than the force). Works well for teams who prefer a fixed-power approach.
Spring-loaded: Compact and fast to reset. Requires precise spring calibration and wears with repeated use. Good for experienced builders.
The calibration process: this is where Trajectory is won or lost
On competition day, you are given a target distance you have never seen. You must be able to predict how to configure your device to hit it.
This requires a calibration table — a lookup chart built from pre-competition test firings:
| Angle (°) | Tension setting | Measured distance (ft) |
|---|---|---|
| 30 | 3 | 8.2 |
| 35 | 3 | 10.1 |
| 40 | 3 | 11.8 |
| 45 | 3 | 13.0 |
| ... | ... | ... |
With enough data points, you can interpolate between values to configure for any target within your range. Teams that arrive at a tournament with a complete calibration table and a device that performs consistently with that table are positioned to score well regardless of which target distance is revealed.
How many test launches does this take? Competitive teams typically do 80–150 test launches over a season to build a reliable table and understand their device's variance.
Common mistakes
Only practicing at one distance. Your device needs to be calibrated across the full event range, not just the one distance you happen to practice at most often.
Not tracking data. If you do not write down every test launch result, you cannot build a reliable calibration table or identify when your device is drifting.
Tubing/spring degradation. Elastic components lose tension over time. If you calibrated in October and launch in March without recalibrating, your table is wrong.
Underestimating variance. A device that lands within 10 cm on average but varies ±40 cm between shots will score poorly. Consistency matters more than average accuracy.
Scoring
Trajectory is scored by distance from target. Closer is better. Most tournaments also award bonus points for a bullseye or for landing within a small radius of the target.
The scoring formula varies by year and tournament, but the principle is consistent: every centimeter matters. A device with low variance — even if its average is 5 cm off — will often outscore a device with a better average but high variance.
SEALS Academy coaches Trajectory and other SciOly build events. Our sessions focus on the physics behind the event, device calibration methodology, and data-driven preparation.