Projectile motion with a ball and a tape measure
A 30-minute hands-on activity that pairs with Launch Lab, with questions to ask along the way.
Launch Lab lets you test hundreds of throws in a few minutes. This activity brings the same idea outside, where the results are messier and more memorable. It works for one learner at home or a class of thirty.
Time: about 30 minutes · Level: beginner · Space: a park, playground or school field
What you need
- A soft ball, such as a tennis ball or a beanbag
- A long tape measure, or a ball of string marked every metre
- Chalk, cones or small stones to mark landing spots
- A protractor, or the angle guide printed below
- A notebook or the table at the end of this page
Before you go outside: play first
Have everyone play Missions 1 and 2 in Launch Lab. Then ask one question and write down their answers:
"If you throw as hard as you can, which angle will go the farthest?"
Most people guess very high or very low. Keep their guesses. You'll come back to them.
The experiment
- Pick a thrower and a throwing line. Use one person for all throws so the speed stays roughly the same.
- Throw at three angles: low (about 20°), middle (about 45°) and high (about 70°). Throw each angle three times.
- Mark every landing spot and measure its distance from the line.
- Take the middle value of the three throws for each angle. This cancels out the odd wild throw.
- Compare with the guesses from before.
Underarm lobs are easier to repeat than full overarm throws. Consistency matters more than power here.
Questions to ask along the way
These follow the order of the game's missions, from simple to harder.
- While throwing: "Which throw stayed in the air the longest? Was it also the one that went farthest?"
- After measuring: "Why do you think the middle angle won?" Listen for ideas about time in the air and going forward.
- Stretch: "Two of our angles might land close together. Which two, and why?" (Angles that add up to 90° pair up.)
- Big stretch: "What would happen if we did this on the Moon?" Then open Free Play in Launch Lab and switch planets to check.
What you will probably find
Real throws are rarely perfect. Air slows the ball down, and arms aren't machines. Expect the best real-world angle to come out a little lower than 45°, often around 35° to 40°. This is a great moment to talk about why scientists use models: the game shows the idea without air, and the field shows the real world with it.
Simple recording table
| Angle | Throw 1 | Throw 2 | Throw 3 | Middle value |
|---|---|---|---|---|
| About 20° | ||||
| About 45° | ||||
| About 70° |
Link back to the explainers
After the activity, anyone who wants the maths can read Why 45° throws the farthest. It has a live launcher and the one-line formula behind it. Anyone who wants to stay hands-on will enjoy Same throw, four planets.
Safety
Use soft balls only, keep a clear landing zone, and have measurers stand to the side rather than in front of the thrower.