Two buses from a bus station

What the experiment shows

The buses leave a common point in opposite directions. The red lines stand where the gap between them reaches the given distance.

How to run it

1. Run the scene: the two move apart, and the S caption shows the distance between them.
2. Enter your answer in the Task panel and press “Check”.
3. Change the speeds or the time with the sliders and solve again.

Questions to discuss

• Why are the speeds added when moving in opposite directions too?
• How does the distance change if the time doubles?

The science

Every hour the gap grows by the sum of the speeds: the speed of separation. The distance is S = (v₁ + v₂) · t and the time is t = S / (v₁ + v₂).

Try it at home

Stand back to back with a friend and walk 10 steps each in opposite directions: how many steps apart are you?

What to change in the editor

• In the editor flip one participant to get a same-direction or catch-up problem.
• Add a caption with each participant's distance from the start.