Scalars Have Magnitude Only, Vectors Have Direction Too

Steps:

• Define scalars as quantities with magnitude alone (no direction) and vectors as those with both magnitude and direction.
• Check acceleration: it involves change in velocity, which has direction, making it a vector.
• Check force: it acts in a specific direction, as per vector addition in physics.
• Check kinetic energy and momentum: energy uses speed squared (magnitude only), while momentum uses velocity (direction included).

Why C is correct:

• Kinetic energy formula $KE = \frac{1}{2}mv^2$ depends solely on mass and speed magnitude, not direction, defining it as scalar.

Why the others are wrong:

• A: Acceleration is a vector, as $\vec{a} = \frac{d\vec{v}}{dt}$ includes directional change.

Final answer: C