alleryAccording to Galileo's law of inertia, an object moving on a frictionless horizontal plane will:
ADecelerate and eventually stop
BContinue to move with constant velocity
CAccelerate uniformly forever
DOscillate about its starting point
Answer & Solution
Correct answer: B. Continue to move with constant velocity
1. Galileo concluded from inclined-plane experiments that motion on a frictionless horizontal plane is intermediate between acceleration (down-slope) and retardation (up-slope).
2. Without friction or any unbalanced force, the body neither speeds up nor slows down.
3. Therefore it must continue with constant velocity — the principle of inertia.
4. Newton later codified this as the First Law of Motion.
_Source: syllabus Physics Ch 4 "Laws of Motion", §4.3 The Law of Inertia, p. 50_
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