Difficulty: Easy
Correct Answer: True
Explanation:
Introduction / Context:In introductory mechanics, the term “retardation” is commonly used to describe acceleration that reduces the magnitude of velocity. Sign conventions can be confusing, so this statement needs careful interpretation.
Given Data / Assumptions:
Concept / Approach:Retardation (deceleration) is any acceleration that acts opposite to the direction of velocity, thereby reducing speed. When motion is in the positive direction (v > 0) and acceleration is negative (a < 0), the acceleration is retarding. Many elementary texts equate “negative acceleration” with “retardation” under this typical convention.
Step-by-Step Discussion:
Choose positive x upward or to the right; suppose v > 0.If a < 0, speed decreases ⇒ this is deceleration/retardation.If v < 0 (moving in negative direction) with a > 0, acceleration is still retarding because it opposes velocity—even though its sign is positive. Thus, strictly speaking, “retardation” is about opposing velocity, not merely the sign.However, in many exam contexts, “negative acceleration” is accepted as “retardation” relative to a chosen positive velocity direction.Verification / Alternative check:Consider free fall upward throw with upward positive: a = −g. During ascent, speed reduces; the negative acceleration is retarding. During descent (v negative), the same a = −g increases the speed (not retarding), illustrating the nuance.
Why Other Options Are Wrong:
Common Pitfalls:Assuming sign alone defines retardation without checking the direction of velocity. Always compare acceleration direction with velocity direction.
Final Answer:True
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