The difference between speed and velocity lies primarily in the role of direction:
- Speed is a scalar quantity that measures how fast an object is moving, regardless of direction. It is the rate at which an object covers distance. Speed only has magnitude (a numerical value) and is always positive or zero. For example, a car traveling 50 km/h has a speed of 50 km/h.
- Velocity is a vector quantity that measures both how fast an object is moving and in which direction. It is the rate of change of the object's position (displacement) with respect to time. Velocity has both magnitude and direction. For example, a car traveling 50 km/h west has a velocity of 50 km/h west.
In summary:
- Speed = distance traveled / time (no direction)
- Velocity = displacement / time (includes direction)
Because velocity includes direction, it can change even if the speed remains constant, such as when an object moves along a curved path. Speed, however, does not change with direction changes as long as the magnitude of motion is the same. Thus, while speed tells you how fast something is moving, velocity tells you how fast and in what direction it is moving. This distinction is fundamental in physics to describe motion accurately. This explanation is consistent with physics educational sources such as Vedantu, The Physics Classroom, Britannica, and others.
