Dumbbell collars and liquid-propellant rocket engine: what they have in common

1. Step 1. Dumbbell collars — is part of — Dumbbell. They secure the discs.
2. Step 2. Dumbbell — uses — Universal gravitation. Weight.
3. Step 3. Universal gravitation — is used in — Water tower. Pressure from height.
4. Step 4. Water tower — has part — Centrifugal pump. Filled by pumps.
5. Step 5. Centrifugal pump — is part of — Liquid-propellant rocket engine. Turbopumps deliver the propellant.

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