Scientists Say: Velocity

This is the speed of an object in a given direction

Our cars keep track of how fast you are driving — your speed. But a speedometer doesn’t tell you your velocity. It would have to tell you both the speed and the direction you are traveling.

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Velocity (noun, “veh-LAH-sih-tee”)

Velocity is the speed an object is traveling in a specific direction. It’s easy to confuse speed and velocity, but they aren’t quite the same thing. Speed is how quickly an object covers a distance. For example, a car might be going 50 kilometers (31 miles) per hour. That is its speed. But its velocity is the car’s speed and its direction. So if the car is going 50 kilometers per hour to the north, that’s its velocity.

Velocity is a mathematical vector. That means it has both a magnitude (speed) and a direction. Scientists need to consider an object’s velocity to calculate its momentum — its velocity multiplied by its mass. Scientists use measures of velocity in everything from figuring out how much rain is falling to sending a rocket to space.

In a sentence

Small raindrops fall at a higher velocity than large ones — so fast, they break the speed limit.

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Bethany Brookshire is the staff writer at Science News for Students. She has a Ph.D. in physiology and pharmacology and likes to write about neuroscience, biology, climate and more. She thinks Porgs are an invasive species.

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