Electric toothbrush and railway track: what they have in common

1. Step 1. Electric toothbrush — is made of — Nylon. The bristles are nylon.
2. Step 2. Nylon — evolved into — Polyester. The next synthetic fibre.
3. Step 3. Polyester — is material for — Tensile structure. A diaphragm.
4. Step 4. Tensile structure — has part — Wire rope. Cables.
5. Step 5. Wire rope — is part of — Funicular. A cable.
6. Step 6. Funicular — uses — Railway track. Rails.

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