Which of the following best describes the difference between a vector and a scalar quantity?

• A. A vector is measured in $m$ (meters), while a scalar is measured in $s$ (seconds).
• B. A vector is always $+$ (positive), while a scalar can be $-$ (negative).
• C. A vector has only magnitude, while a scalar has both magnitude and direction.
• D. A vector has both magnitude and direction, while a scalar has only magnitude.

Answer: (D)

Verified step by step guidance

1. Step 1: Understand the definitions of scalar and vector quantities. A scalar quantity is defined by only its magnitude (size or amount), such as temperature or mass.
2. Step 2: Recognize that a vector quantity has both magnitude and direction, meaning it not only has a size but also points in a specific direction, such as velocity or force.
3. Step 3: Identify that the units of measurement (like meters or seconds) do not determine whether a quantity is scalar or vector; rather, it is the presence or absence of direction that matters.
4. Step 4: Note that vectors can have positive or negative components depending on their direction, so the sign alone does not distinguish vectors from scalars.
5. Step 5: Conclude that the key difference is that vectors have both magnitude and direction, while scalars have only magnitude.