Two pedestrians toward each other

What the experiment shows

Two pedestrians set off at the same time from two points toward each other. The scene time is stretched so the slow meeting is easy to watch.

How to run it

1. Run the scene and watch the S caption: the distance between them shrinks steadily.
2. Enter your answer in the Task panel and press “Check”.
3. Move the sliders and solve again: the statement updates itself.

Questions to discuss

• Why are the speeds added when moving toward each other?
• How does the meeting time change if the distance doubles?

The science

Every hour the gap shrinks by the sum of the speeds: the closing speed. The meeting time is the distance divided by the closing speed: t = S / (v₁ + v₂).

Try it at home

Mark two points 20 steps apart on the pavement and walk toward each other with a friend, comparing how many steps each took.

What to change in the editor

• Open the example in the editor and swap the participants for other shapes, changing the speed scale.
• Add a “delay” variable and let one leave later to get a catch-up problem.