A boat downstream: how far does it go
A river motion problem with sliders: own speed, current and time. Run the boat, find the distance and check your answer.
2D
Age 10+10 min
Motion problems
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Press “Run”. Bodies move by the laws of physics: gravity, friction, elasticity.
What the experiment shows
The boat goes downstream, so the current helps it. Sliders set the own speed, the current and the travel time, and the finish mark stands where the boat will be after that time.
How to run it
- Run the scene: the boat reaches the finish mark exactly at the chosen time.
- Work out the distance and enter it in the Task panel.
- Set the current to 0 and compare: how did the distance change?
Questions to discuss
- Why is the current added to the boat's own speed?
- What happens to the distance if the boat goes upstream?
The science
Downstream the boat's speed is its own speed plus the current: v = v₀ + vc. The distance is S = v · t.
Try it at home
Float a paper boat in a stream or in a tub with a hose current and time it over one metre.
What to change in the editor
- In the editor flip the boat and bind its speed to v₀ − vc to get the upstream case.
- Add a second boat with a different speed and make a race.