Which quantity describes both speed and direction of motion?

Which quantity describes both speed and direction of motion?

• A. Velocity
• B. Speed
• C. Displacement
• D. Acceleration

Answer: (A)

Velocity describes both how fast and in what direction an object is moving because it is a vector quantity that combines speed (magnitude) with direction. It is defined as the rate of change of position, v = displacement per time. For example, a car moving east at 60 km/h has velocity 60 km/h east. Speed alone is just how fast, without any direction. Displacement gives a direction for the straight-line distance from start to end but doesn’t tell you how long the journey took. Acceleration describes how velocity changes over time, not the current state of motion. So velocity is the quantity that captures both speed and direction.

Velocity describes both how fast and in what direction an object is moving because it is a vector quantity that combines speed (magnitude) with direction. It is defined as the rate of change of position, v = displacement per time. For example, a car moving east at 60 km/h has velocity 60 km/h east. Speed alone is just how fast, without any direction. Displacement gives a direction for the straight-line distance from start to end but doesn’t tell you how long the journey took. Acceleration describes how velocity changes over time, not the current state of motion. So velocity is the quantity that captures both speed and direction.