velocity

/vəˈlɒsəti/ (bre, ipa) · /vəˈlɑːsəti/ (ame, ipa) · /və-ˈlä-sə-tē -ˈlä-stē/ (ame, mw)

velocity — noun

  • velocitysingular
  • velocitiesplural

1. a measurement of how fast an object or person moves, usually from one point to a

1.名詞B2
釋義

a measurement of how fast an object or person moves, usually from one point to another through air, water, or space

例句

The wind velocity reached 130 kilometres per hour during the storm.

collocation: wind velocity

Sahil measured the velocity of the river current before the kayak race began.

velocity + of + [object] for measuring how fast

同義詞
  • speed

    Everyday word for how fast something moves; less formal than velocity

  • pace

    Used especially for steady, repeated movement like walking or running

  • rate

    Focuses on how fast something happens or changes over time

反義詞
  • slowness

    The quality of moving at low speed

文法句型

velocity + of + [something]

at + [adjective] + velocity

用法筆記

More formal than 'speed'. Common in weather reports, engineering, and news. In casual conversation, 'speed' is preferred.

常見錯誤

❌The car's velocity was very fast.
✅The car was moving at high velocity.
💡'fast' describes the object, not the velocity measurement itself.
❌The wind blew at a high speed velocity.
✅The wind blew at high velocity.
💡'velocity' already means speed; using both is redundant.

2. a measurement that combines how fast an object moves with the specific direction

2.名詞B2
釋義

a measurement that combines how fast an object moves with the specific direction it follows, used especially in physics and engineering

例句

Talia calculated the velocity of the car moving north at sixty kilometres per hour.

velocity includes direction — vector quantity

When Hari turned the car left at the traffic lights, its velocity changed even though the speed stayed the same.

concrete: direction change at an intersection

同義詞
  • speed

    Only measures how fast; does not include direction

  • momentum

    Combines velocity with mass; a physics quantity that measures motion in a direction

文法句型

velocity + of + [object] + [direction]

at + [number] + [direction] + velocity

用法筆記

In physics, velocity is a vector quantity that requires direction. If no direction is given, use 'speed' instead. Distinguish from sense 1 (GENERAL SPEED), which measures only how fast.

常見錯誤

❌The velocity of the plane is 900 km/h.' (in a physics task, with no direction given)
✅The velocity of the plane is 900 km/h heading west.
💡In physics, velocity must include direction; otherwise use 'speed'.
❌Speed and velocity are the same thing.
✅Speed tells you how fast something moves; velocity also tells you which way it is going.
💡They are different concepts in physics.