What is the difference between speed and velocity?

Speed and velocity are both measures of motion, but they convey different types of information about an object’s movement. Here are the primary differences:


Speed: This is a scalar quantity that refers to “how fast an object is moving.” It provides only the magnitude of the motion and is typically measured in units like meters per second (m/s) or kilometres per hour (km/h). For instance, if a car is moving at 50 km/h, we’re only considering the magnitude of its motion.

Velocity: This is a vector quantity that gives both the speed of an object and its direction. Thus, velocity has both magnitude and direction. For instance, if that same car is moving at 50 km/h to the east, its velocity provides more specific information about its motion.


Speed: Has no direction; it’s just a magnitude.

Velocity: Has a specific direction. Two objects can have the same speed but different velocities if they are moving in different directions.


Speed: Is calculated as the distance traveled divided by the time taken.

Velocity: Is calculated as the displacement (change in position) of an object divided by the time taken. Displacement is a vector quantity and takes into account the initial and final positions and the path taken.


Example 1: If you run around a circular track and complete one full loop, your speed might be constant (assuming you run at a consistent pace), but your velocity is continuously changing because its direction is changing as you move around the circle.

Example 2: If you drive 100 meters straight forward and then 100 meters straight back to your starting point, your average speed would be the total distance (200 meters) divided by the time taken. But your average velocity would be zero because your overall displacement (change in position) is zero.

In summary, while speed gives us a simple measure of how fast something is moving, velocity provides more detailed information about the nature of an object’s motion, including its direction.

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