Rocking horse and incandescent light bulb: what they have in common

1. Step 1. Rocking horse — uses — Pendulum. Rocking.
2. Step 2. Pendulum — uses — Newton’s laws. The swing is described by Newtonian mechanics.
3. Step 3. Newton’s laws — includes — Reaction force. Reaction is Newton’s third law.
4. Step 4. Reaction force — is used in — Ion thruster. Jet thrust.
5. Step 5. Ion thruster — is made of — Tungsten. The cathodes are tungsten.
6. Step 6. Tungsten — is material for — Incandescent light bulb. A tungsten filament (since 1904–1910).

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