MCQ practice · SSC Physics Board questions · Chapter 3: Force
Rocket motion is an example of what?
Think it through first, then pick an option.
- a the law of conservation of momentum
- b Newton's second law
- c the law of motion
- d Newton's first law
Answer and explanation
Correct answer: a the law of conservation of momentum
The gas leaves the rocket downward at great speed. The total momentum starts at zero, so the rocket gains equal and opposite momentum and rises, just like a gun's recoil.
Why the other options are wrong
- b Newton's second law: The second law links force and acceleration. A rocket throws gas down and gains an equal and opposite momentum, which is conservation of momentum.
- c the law of motion: “The law of motion” is not a specific law; the specific explanation of rocket motion is conservation of momentum.
- d Newton's first law: The first law is about inertia; the rocket rises from rest against the gas's momentum, so this is not an inertia example.
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