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Inertia and Newton's first law

Aviation Mechanic General (AMG) practice question 18 of 20 on Physics for Aviation. ACS element AM.I.J.K5 · difficulty: recall. Want to answer it in a timed quiz? Use the Aviation Mechanic General (AMG) practice mode.

Question bank updated 2026-09-22

QUESTIONPassengers are thrown forward in their seats when an airplane is brought to a sudden halt in the parking area. This discomfort is a demonstration of

  1. Amomentum change, described by Newton's second law
  2. Binertia, described by Newton's first law
  3. Caction and reaction, described by Newton's third law
Show the answer and explanation

Correct answer: B. inertia, described by Newton's first law

  • A — incorrect Newton's second law relates the rate of change of momentum to the applied force and is the basis of the thrust formula. The handbook attributes the passengers being thrown forward to inertia under the first law.
  • B — correct Newton's first law states that objects in motion tend to remain in motion at the same speed and direction unless acted on by an external force. The passengers' bodies keep moving forward when the airplane stops; this property of matter is inertia.
  • C — incorrect The third law concerns equal and opposite force pairs, such as a propeller pushing air backward and the air pushing the blades forward. It is not the law that describes the tendency to keep moving.

BACKGROUND

Inertia is a property of matter described by Newton's first law of motion: objects at rest tend to remain at rest, and objects in motion tend to remain in motion at the same speed and in the same direction, unless acted on by an external force. The handbook illustrates it with a magician pulling a tablecloth from under dishes and with passengers thrown forward when an airplane stops suddenly. Newton's second law states that when a force acts on a body, the rate of change of its momentum is proportional to the applied force, which leads to Force = Mass × Acceleration. Newton's third law states that for every action there is an equal and opposite reaction.

STUDY TIP

Match each law to its keyword: first law is inertia, second law is force equals mass times acceleration, third law is action and reaction.

KEY POINTS

  • Newton's first law describes inertia
  • Objects keep their state of rest or motion unless an external force acts
  • Passengers lurching forward at a sudden stop illustrate inertia

SOURCES

  • FAA-H-8083-30B ch05 "Newton's Law of Motion" (First Law)
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SkyDrill is not affiliated with the FAA. This is an original practice item based on FAA-H-8083-30B Aviation Maintenance Technician Handbook – General, 14 CFR part 43 and part 65. Regulations and handbooks are revised; confirm details against the current edition.