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Difference Between Speed and Velocity

Published October 24, 2021

Speed and velocity are two words that we use interchangeably, but they actually have very different meanings. Speed is the distance traveled per unit of time (in other words, miles or km per hour). Velocity is an object's speed and direction at a given moment in time (in other words, meters per second).

This difference may seem small to some people; however, it has large implications on how we apply these terms to physics problems. This blog post will help you understand the difference between these two terms, so you can be more informed when reading about physics or talking to your friends.

What is Speed?

The definition for speed is relatively simple; however, we will go into more depth to help you better understand speed. Imagine that you are driving a car. You want to know how fast you are going, so you check the speedometer. The speedometer tells you that your current speed is 55 miles per hour (55 mph). This number indicates that at this given speed, you are traveling a distance of 55 miles every hour. In this example, speed is how far an object travels in one unit of time (in other words, it tells us how fast we are going).

What is Velocity?

Now that we have an understanding of speed, let's talk about velocity. Velocity is the combination of how fast something is traveling and which direction it travels in at any given moment in time. This means that if you are driving 55 mph due east on a highway, your velocity would be expressed as 24.6 meters per second (m/s).

This example illustrates that when both speed and direction are taken into account, your car has a velocity of 24.6 m/s. Even though an object may be traveling at a certain speed, its velocity may cause the object to move in different directions.

Differences Between Speed & Velocity

The difference in Formula & measuring unit

The most accepted formula for speed is the distance traveled per unit of time. The formula for velocity is an object's speed and direction at a given moment in time. Speed is measured in miles per hour (mph) or kilometers per hour (km/h). Velocity is measured using meters per second (m/s). The key thing that differentiates both of them is the fact that Speed is calculated by knowing the distance. While Velocity is calculated by knowing the displacement.

The difference in values

Another key difference to note is the fact that Speed can never be zero or negative & is always positive. Velocity on the other hand can be positive, negative, or zero. An object's velocity is always undefined when it is traveling at the speed of light due to relativity (the faster you are going, the harder time an outside observer has to measure your acceleration).

The difference in direction

Speed tells us how fast something moves regardless of which way it moves. Velocity on the other hand describes both where and how fast something moves depending on its orientation relative to some frame of reference. For example, if you are driving 55 mph due west on a highway, your velocity is 24.60 m/s (24.60 km/h).

Speed can only ever change if we alter the reference frame we are using to describe it. This means that speed is a relative measurement and can only be determined by comparing two separate frames of reference. Velocity on the other hand describes both how fast something moves & which direction it moves in within any given reference frame.

Comparison Chart

ParametersSpeedVelocity
QuantityScalarVector
Can be negativeNoYes
Can be zeroNoYes
Calculated asmph or kphm/s
Direction dependentNoYes
Formulas = d/tv = dis/t
Dependent onDistanceDisplacement

Similarities between Speed & Velocity

The biggest similarity between Speed and Velocity is the fact that both can be measured. Also, both calculations are based on a moving body's displacement. Displacement is the term used to describe how far an object moved in a certain direction (in other words, it tells us where an object has traveled).

FAQs

What are some practical applications of Speed?

Practical applications for speed include calculating the time it takes to travel somewhere or how far an object has moved. These calculations are found daily in GPS systems and other speed-based applications.

What are some practical applications of Velocity?

Practical applications for velocity include calculating how much an object will move if it is accelerated or the time it takes to stop moving at a certain rate. These calculations can be seen every day when driving cars, riding bikes, etc.

Velocity is used in many fields including physics, sports, robotics, etc. Engineers may use velocity when designing vehicles (such as cars) since they rely on acceleration and deceleration during operation (speed does not take direction into account). A physicist might use velocity to calculate changes in something's momentum over a period of time due to forces applied by gravity or friction. Finally, a baseball pitcher would need to know his pitching velocity so he can adjust according to opposing team players' batting abilities/disabilities.

Can you have negative Speed?

No, ideally you cannot have negative speed.

Can you have negative Velocity?

Yes, an object can have negative velocity if it is traveling in the opposite direction of its reference frame.

Conclusion

These two terms are not interchangeable as they each refer to different measurements that describe completely separate concepts. Even though they are used interchangeably in day-to-day life, in Physics both terms cannot be used interchangeably as they are different quantities.

If you treat these words as synonyms or think about them too closely, your understanding may become confused! In order to avoid any confusion with either term, consider carefully what framework we're using when applying this word. And be specific enough so that people understand exactly what idea you're trying to convey.

References

Feel free to comment and discuss about the article in the comment space below if you have any information or remarks to add. If you think we made a mistake, you can also report it there.
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About the Author: Nicolas Seignette

Nicolas Seignette, who holds a scientific baccalaureate, began his studies in mathematics and computer science applied to human and social sciences (MIASHS). He then continued his university studies with a DEUST WMI (Webmaster and Internet professions) at the University of Limoges before finishing his course with a professional license specialized in the IT professions. On 10Differences, he is in charge of the research and the writing of the articles concerning technology, sciences and mathematics.
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