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Two motorcycles on a wet road
Age 12 · Physics
Two motorcycles brake on the same wet road. The faster one leaves a tire mark many times longer than the slower one, so it needs far more room to stop.
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Age 12: open this week
Browse Age 12
In the picture
- The short dark tire mark: the distance covered while braking from a lower speed
- The long dark tire mark: the distance covered while braking from a higher speed
- The puddle under the front wheel: water on the road that reduces tire grip
- A rear wheel on wet asphalt: the point where braking starts and the tire mark begins
Examples
- A bicycle on a rainy street needs much more distance to stop than on a dry one.
- A car following another car too closely cannot stop in time when the one ahead brakes.
Key takeaways
- Doubling the speed makes the braking distance about four times longer.
- A wet road stretches the stopping distance, so leave more space.
Quiz: Two motorcycles on a wet road (Age 12)
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If you double your speed, about how much longer does the braking distance become?
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According to the card, why does a wet road make stopping distance longer?
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On a wet road, what does a higher speed need compared with a lower speed?
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