# What is the difference between speed and velocity kid definition?

Main Difference Between Speed and VelocityIt may seem like the terms speed and velocity mean the same thing. But if youre studying physics, its important to know the difference bet

## Main Difference Between Speed and Velocity

It may seem like the terms speed and velocity mean the same thing. But if youre studying physics, its important to know the difference between these two concepts. Keep reading to learn the main difference between speed and velocity and what information their measurements can tell us.

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## How to Tell Speed and Velocity Apart

Speed and velocity both measure an objects rate of motion. However, speed is a scalar quantity, which means that it can be described with a numerical value. Velocity is a vector quantity, which depends on direction as well as magnitude. Read these definition for more information:

- speed - the rate of distance traveled by a moving object over time
- velocity - the rate of displacement of a moving object over time

Basically, an objects speed tells you how fast its going. Its velocity tells you how fast its going in a certain direction. You use speed measurements in your daily life, but physicists depend on velocity measurements more frequently in their work.

## How Speed Works

There are two ways to measure an objects speed: its average speed and its instantaneous speed. The average speed tells you the average measurement of how fast it was going over a period of time. Its instantaneous speed tells you how fast its going in a single instance.

There are three units to measure speed:

**m/s**- meters per second (used by The International System of Units and Measurements)**kph**- kilometers per hour (used by countries that use the metric system)**mph**- miles per hour (used in the United States)

There are several tools that measure an objects speed. Tachometers measure an engines speed in rpms (revolutions per minute) and speedometers measure the speed in an automobile. RADAR can also measure the speed of a moving object from a distance.

## How Velocity Works

Velocity depends on the direction an object travels. It incorporates the speed of that object as well as the difference between its starting place and its ending place. You use the same units for speed (m/s, kph, and mph) when measuring velocity, but factoring in its direction.

You need to calculate the velocity of objects when determining where they might go. Like speed measurements, velocity can be measured by an objects average velocity and its instantaneous velocity.

## Equations for Speed and Velocity

Its easiest to see the difference between speed and velocity when you compare their equations. In order to measure an objects speed (s), you measure its distance (d) over time (t):

s = d/t

Once you know the objects speed, you can calculate its average velocity by calculating the change in displacement (d) over the change in time (t):

v = Δs/Δt

This information may not seem as straightforward for an everyday traveler, but when studying physics, its very important to know the difference between an objects speed and velocity. When they are the same value, the object has traveled in a straight line. Different values between speed and velocity indicate that the objects path was not straight.Advertisement

## Measuring Our Lives With Physics

Knowing how fast youre going or are capable of going is helpful for drivers, cyclists, runners, and anyone who can read a speedometer. But speed is just the starting point for many valuable concepts in physics. Check out additional resources on velocity, including more examples of scalar and vector quantities and how velocity differs from acceleration.

## Jennifer Gunner

Staff Writer