Trebuchet and oil well: what they have in common

1. Step 1. Trebuchet — uses — Counterweight. A falling counterweight swings the throwing arm.
2. Step 2. Counterweight — is used in — Tower crane. A counterweight balances the jib.
3. Step 3. Tower crane — has part — Block and tackle. The load is lifted with a block and tackle.
4. Step 4. Block and tackle — is part of — Drilling rig. The block and tackle lifts the drill string.
5. Step 5. Drilling rig — is used in — Oil well. A well is drilled by a rig.

Open Evothings