Difficulty: Easy
Correct Answer: Speed
Explanation:
Introduction / Context: Physical quantities are classified as scalars (magnitude only) or vectors (magnitude and direction). Correctly identifying which is which is fundamental to solving mechanics problems correctly.
Given Data / Assumptions:
Concept / Approach: A scalar quantity is fully described by a number and appropriate unit, with no directional attribute. A vector quantity requires both magnitude and direction and follows vector addition rules.
Step-by-Step Solution:
Force requires magnitude and direction and adds vectorially ⇒ vector. Velocity describes rate of change of displacement with direction ⇒ vector. Acceleration describes rate of change of velocity with direction ⇒ vector. Speed is the rate at which distance is covered, with no directional component ⇒ scalar.Verification / Alternative check: Speed is the magnitude of velocity. Magnitude alone is scalar; only when direction is attached (velocity) does it become a vector.
Why Other Options Are Wrong: Force, velocity, and acceleration inherently require direction to be fully specified and obey vector laws (e.g., parallelogram rule). Hence they are vectors, not scalars.
Common Pitfalls: Confusing speed with velocity; thinking that “fast” implies a direction; treating acceleration as “just speeding up” rather than a vector that can also indicate slowing or turning.
Final Answer: Speed.
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