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Which law of motion explains why a rocket moves forward when hot gas shoots out of its back?

Newton's third law: every action has an equal and opposite reaction.

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  1. Newton's third law ✔
  2. Kepler's first law
  3. Ohm's law

Why: The engine pushes exhaust one way, and the exhaust pushes the rocket the other way. That push is thrust, and it works because of the equal and opposite reaction.

Huh, didn't know that: Rockets use liquid or solid fuel, and the space shuttle used both, with liquid main engines and two solid side boosters.

The dad joke
How do you put a baby astronaut to sleep? You rocket.
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References

Answer: Newton's third law. The engine pushes exhaust one way, and the exhaust pushes the rocket the other way. That push is thrust, and it works because of the equal and opposite reaction.

  1. NASA: What Is a Rocket? www.nasa.gov/learning-resources/for-kids-and-students/what-is-a-rocket-grades-5-8
    When the rocket pushes out its exhaust, the exhaust also pushes the rocket.
    Checked 2026-10-10.

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