Speed vs Velocity – What’s the Difference?

When we think of speed and velocity, the two words appear to be quite similar. Both words relate to how quickly a body moves from one point to another, introducing an element of time. But there is a difference between speed and velocity, and it is important to know how the concepts differ.

What is Speed?

Speed is the rate at which an object moves from one point to another. It is usually expressed in units of distance divided by time, for example km/h, m/s, etc. It does not matter in which direction an object is going or whether it is changing its direction – all that matters is that it is going.

Speed is a scalar quantity and thus can be represented by a single value, such as 60km/h. This means that speed is completely described by its magnitude; we don’t care which direction it is in.

What is Velocity?

Velocity is the rate at which an object changes its position. Besides the speed, velocity also includes the direction of an object’s motion. This means that while speed is completely described by its magnitude, velocity is described by both its magnitude and the direction.

Due to this, velocity is a vector quantity, which can be represented using both magnitude and direction – for example, 60km/h East.

Speed vs Velocity

The main difference between speed and velocity is that speed does not take into account the direction of an object’s motion, whereas velocity does. This is why velocity is considered a vector quantity, while speed is a scalar quantity.

Additionally, in physics, speed is usually measured in nonlab frame of reference, which implies that we don’t take into account the movement of the observer. Velocity, on the other hand, is usually measured from the lab frame of reference and thus takes into account the observer’s motion.

In summary, speed is a scalar quantity which is only described by its magnitude, while velocity is a vector quantity which is described by both its magnitude and the direction.