## PHYSICS LESSON--

When Millipede Meets Train

### Yet another tool for teachers

Sometimes, students complain that physics is neither practical nor fun. That claim can be countered in many ways. The real-life example described here shows that physics can indeed be practical. Even the most jaded student will enjoy using his or her analytical skills to better understand what happens when millipedes try to cross a train track .

#### The Millipedes and the Train

An article in the August 19, 2000 issue of New Scientist gives the real-life components of this physics lesson:

According to a report in the Yomiuri newspaper, an express train north of Tokyo was brought to a halt last week when "clusters of millipedes" tried to cross a 300-metre section of track. The train "squashed out their bodily fluids, which apparently acted as a lubricant, making the wheels slip", the paper says. It took two and a half hours to resume services and hundreds of passengers had their journeys delayed.

*(Thanks to Sally Shelton for bringing this to our attention.)*

Those are the facts. Now for the challenging problem

#### The Physics of the Situation

Here is the physics problem, presented in 4 parts:

1. Prepare a force diagram showing the interaction of a millipede and a train.

2. Calculate the exact forces involved.

3. Calculate how many trains are necessary to stop a millipede.

4. Calculate how many millipedes are necessary to stop a train.

© Copyright 2000 Annals of Improbable Research (AIR)

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