Iron-capped battering log and archimedes’ screw: what they have in common

1. Step 1. Iron-capped battering log — is part of — Battering ram. A heavy log with a metal-clad head.
2. Step 2. Battering ram — works like — Pile driver. A battering ram and a pile driver both strike with a heavy weight: one breaks gates, the other drives piles.
3. Step 3. Pile driver — has part — Block and tackle. Lifting the weight.
4. Step 4. Block and tackle — has part — Pulley. A block and tackle is several pulleys and a rope.
5. Step 5. Pulley — is a kind of — Simple machine. A pulley is a simple machine.
6. Step 6. Simple machine — includes — Archimedes’ screw. A classic example of using the screw.

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