Lesson 11 · 60 minutes
Getting Off the Line
Acceleration, slip, and why fast starts are slow
Today's goal
Find the fastest launch your robot can make without slipping, and prove it is faster overall than a harder launch.
Ideas in this lesson
- Traction is a budget: spend it all on acceleration and none is left for steering
- A wheel that slips is doing no useful work
- Fastest to full speed is not the same as fastest to the far wall
- Acceleration curves: gentle at the start, brisk once rolling
Sense → Think → Do
DO, examined closely. Same command, different ramp, different outcome.
How the session runs
- Open Calibrate → Step 0. Set the seed slider low and watch a launch. The robot should creep, then build.
- Turn the seed up until you can hear a chirp or see the nose twitch sideways at the start. That is slip.
- Back off one notch. Write down the two numbers.
- Race two settings over three metres: the slipping launch versus the clean one. Time both.
- Explain the result. Most groups find the clean launch wins or ties — the slipping robot spent its first moments going nowhere and pointing wrong.
Sample program
Full speed to the far end and back. Run it at a gentle ramp and at a harsh one, and time both round trips.
V 9 F 3000 W 500 B 3000
Paste it into the Workshop's Robot language box, then press Text → blocks to see it as blocks — or just send it straight to the robot.
Try this
- Does the best setting change on carpet? Predict first, then measure.
- Add a passenger (a book taped on top). Does the extra weight help traction or hurt acceleration?
- Time a straight sprint and a slalom with the same settings. Does the best launch differ for the two?
When it goes wrong
| What you see | What it means |
|---|---|
| The robot lurches sideways at the start | One wheel gripped before the other. Lower the seed until both wheels start together. |
| It takes forever to reach speed | Growth is too low. The seed controls the first push; growth controls how quickly it builds after. |
Notes for the grown-up
The counter-intuitive result is the point: the aggressive setting feels faster and loses. This is the same trade-off as a dragster wheelie or a sprinter's start, and kids who have raced anything will recognise it immediately.