Magnetism and bicycle: what they have in common

1. Step 1. Magnetism — is used in — Hard disk drive. Magnetic recording.
2. Step 2. Hard disk drive — has part — Ball bearing. Bearings (later fluid-dynamic ones).
3. Step 3. Ball bearing — is part of — Bicycle. Ball bearings in the hubs and bottom bracket let the wheels and pedals spin easily.

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