Which statement is true about velocity and speed regarding signs?

• A. Speed can be negative.
• B. Velocity can be negative if moving in a negative direction; speed is always non-negative.
• C. Velocity is measured in kilometers per second only.
• D. Speed changes with direction.

Answer: (B)

Velocity is a vector, so it carries both how fast and which way. The sign of velocity encodes direction along a chosen reference axis: moving in the positive direction gives a positive velocity, while moving in the opposite direction gives a negative velocity. Speed, in contrast, is a scalar and represents only how fast you’re going, with no direction attached, so it is always non-negative. For example, traveling at 5 m/s to the right has velocity +5 m/s and speed 5 m/s, while the same motion to the left has velocity -5 m/s but speed still 5 m/s. Units can vary, so velocity isn’t limited to kilometers per second. Speed changing with direction isn’t a defined feature—speed is just the rate of motion, whereas velocity changes sign when direction changes.