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

• A. A scalar quantity is always measured in $m$eters, while a vector quantity is always measured in $s$econds.
• B. A scalar quantity can be negative, but a vector quantity cannot.
• C. A scalar quantity has only magnitude, while a vector quantity has both magnitude and direction.
• D. A scalar quantity has both magnitude and direction, while a vector quantity has only magnitude.

Answer: (C)

Verified step by step guidance

1. Understand the definitions of scalar and vector quantities: Scalars are quantities that have only magnitude (size or amount), while vectors have both magnitude and direction.
2. Recognize that scalar quantities include examples like temperature, mass, and time, which do not involve direction.
3. Recognize that vector quantities include examples like displacement, velocity, and force, which require both magnitude and a specific direction to be fully described.
4. Note that the units of measurement (such as meters or seconds) do not determine whether a quantity is scalar or vector; rather, it is the presence or absence of direction that matters.
5. Conclude that the best description is: 'A scalar quantity has only magnitude, while a vector quantity has both magnitude and direction.'