### What is the difference between Speed and Velocity?

##### April 10, 2017

## What is the difference between Speed and Velocity

What is the difference between * Speed and Velocity*?

Speed and Velocity are two frequently used

**derived quantities**in Physics.

But are they same ? If not then what are the basic differences between these two? Let’s find out. But before that let us quickly check the types of physical quantities.

### Types of physical quantities

Length, Mass and Time – Each of these 3 physical quantities doesn’t depend on any other quantity for its measurement. So these 3 are called **Fundamental quantities**.

Other quantities like velocity, acceleration, and force all depend on more than one fundamental quantity for their measurements. These are called **Derived Quantities**. [ like velocity depends on length and time measurement ]

To understand these two, let’s first quickly discuss on 2 quantities: Displacement and Distance.

**Displacement and Distance**

Distance is the length actually traveled on a route while Displacement is the shortest distance (straightline distance) between the initial point and final point of the traveled path.

So if anybody runs a *completely circular route* once then the **Distance** traveled is equal to the circumference of the circle i.e. **2.Pi.R** where R is the radius of the circle (and Pi is 22/7).

At the same time the **Displacement** = 0 because the final point is same as the initial point.

Similarly if the runner runs half of the circular track then the Distance traveled is Pi.R and the Displacement is 2R or Diameter of the circle.

**Difference between Speed and Velocity**

Speed is the distance traveled per unit time = (distance traveled)/(time taken)

And the velocity is displacement per unit time =(displacement)/(time taken)

One more thing, Speed doesn’t need mention of any direction of movement while Velocity needs a direction to be mentioned along with its magnitude. **Velocity is a Vector quantity and Speed is a scalar quantity.**

Only when something moves in a straight line in a fixed direction then at any point in time distance and displacement become equal, henceforth in this case speed and velocity magnitude become equal.

But consider one circular track, Here clearly the difference between distance travelled and displacement will be evident, which finally shows us clearly the difference between velocity and speed.