The key difference between speed and velocity lies in the consideration of direction:
- Speed is a scalar quantity that measures how fast an object is moving, regardless of its direction. It is the rate at which an object covers distance and is always a positive value. For example, 50 km/h indicates how fast a car is moving, but not where it is going. Speed is calculated as total distance traveled divided by the time taken
- Velocity is a vector quantity that includes both the speed and the direction of the object's motion. It measures the rate of change of an object's position (displacement) in a specific direction. For example, 50 km/h west describes velocity because it specifies both how fast and in which direction the car is moving. Velocity is calculated as displacement divided by time, where displacement is the straight-line distance from the starting point to the ending point along with direction
Additional points:
- If an object moves in a circle at constant speed, its velocity is constantly changing because the direction changes, even though the speed remains the same
- An object can have zero velocity but non-zero speed if it returns to its starting point, making displacement zero but distance traveled non-zero
- Speed is commonly used in everyday contexts (e.g., speedometers), while velocity is essential in physics for describing motion precisely
In summary, speed tells you how fast something is moving, while velocity tells you how fast and in which direction it is moving
