velocity
vuh-LOSS-uh-tee
/vəˈlɒs.ə.ti/
The speed of something in a given direction.
Unlike speed, which is a scalar quantity, velocity is a vector quantity that strictly requires both magnitude (speed) and direction.
The story behind the word. Derived from the Latin 'velox', meaning swift or rapid. In the 17th century, early physicists like Galileo and Newton adopted 'velocitas' to mathematically define the rate of motion in a specific direction.
Word relationships
- speed: Speed is simply how fast something moves, whereas velocity is how fast it moves in a specific direction.
Commonly confused with
- acceleration: Velocity is the rate of change of position, while acceleration is the rate of change of velocity itself.
Word family
- velocimeter (noun): An instrument for measuring the speed or velocity of a fluid.
Collocations
- terminal velocity
- escape velocity
- high velocity
- wind velocity
Example sentences
- "The rocket escaped Earth's atmosphere after reaching an escape velocity of approximately 11.2 kilometers per second." Physics calculation
- "The velocity of the river increased rapidly as the channel narrowed through the rocky canyon." River hydrology
Memory hook
Think of a 'velocity' raptor (Velociraptor) running at high speed in a straight line toward its prey. Velocity = Velociraptor's directed speed.
When not to use
Do not use when direction is completely irrelevant or unknown; use 'speed' instead.
Fun facts
- Terminal velocity is the constant speed that a freely falling object eventually reaches when the resistance of the medium prevents further acceleration.
Explore more words
Also appears in
- Technology → Physics & Mechanics
- Time & History → Speed & Pace
- Engineering & Industrial Design → Mechanical Systems & Kinematics
- Engineering & Industrial Design → Aerospace & Aeronautics
- Sports, Athletics & Recreation → Track & Field Athletics
- Sports, Athletics & Recreation → Winter & Ice Sports
- Sports, Athletics & Recreation → Motor & Racing Sports
- Physical Sciences & Cosmology → Classical Mechanics & Motion
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