Which of the following is not a vector quantity?

Mass is classified as a scalar quantity, meaning it only has magnitude and does not have a direction. In physics, scalar quantities are characterized by a single value that represents the size or amount of the quantity (in this case, mass), without any directional component.

In contrast, velocity, acceleration, and force are all vector quantities. Vector quantities have both magnitude and a specific direction associated with them. For example, velocity indicates how fast something is moving and in what direction, acceleration describes the change in velocity per unit time along a specific path, and force represents an interaction that causes an object to change its velocity, also having a specific direction in which that force acts.

Understanding the distinction between scalar and vector quantities is crucial in physics, as it helps in analyzing motion and interactions in both one and two dimensions.