Kinematics terminology – is negative acceleration the same as retardation? Assess the statement: “Negative acceleration is called retardation.”

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:

• A one-dimensional problem with a chosen positive direction.
• Acceleration a can be positive or negative relative to that axis.
• Velocity may be positive or negative depending on motion direction.

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:

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:

• False: too strict; although nuance exists, the statement reflects standard elementary usage.
• Other conditional options introduce unnecessary restrictions.

Common Pitfalls:
Assuming sign alone defines retardation without checking the direction of velocity. Always compare acceleration direction with velocity direction.

Final Answer:
True