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How does a rocket move forward, and where does it work best?
ABy pushing on the air behind it, so it needs an atmosphere
BBy pulling on the air ahead of it, so it needs an atmosphere
CBy pushing on the ground below it, so it needs a launch pad
DBy expelling gas backward, so it works better in a vacuum
Answer & Solution
Correct answer: D. By expelling gas backward, so it works better in a vacuum
1. A rocket exerts a large backward force on the gas in its combustion chamber.
2. By Newton's third law the gas exerts an equal forward reaction force on the rocket.
3. That forward reaction force is called thrust.
4. It is a common misconception that rockets push on the ground or on the air behind them.
5. Rockets actually work better in a vacuum, where the exhaust gases escape more readily.
_Source: OpenStax College Physics (CC BY 4.0), Ch 4 "Dynamics: Force and Newton's Laws of Motion", section 4.4 Newton's Third Law of Motion: Symmetry in Forces_
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