1. **Speed**（速度/速率） -- 最通用的"速度"概念，指物体运动的快慢程度 -- 例：The car reached a speed of 120 km/h（车速达到120公里/小时） -- 翻译提示：中文通常译为"速度"，在物理语境下可与"速率"互换
2. **Velocity**（速度/矢量速度） -- 物理学专用术语，指具有方向性的矢量速度 -- 例：The velocity of the projectile was calculated（计算了抛射体的速度矢量） -- 翻译提示：在专业语境中需强调其矢量特性，可译作"速度矢量"或"矢量速度" ...(以上内容有节略,please sign in for more)500
【Speed】 , 【velocity】 , 【momentum】 , 【impetus】 , 【pace】 , 【headway】 are comparable but not all mutually synonymous terms that basically apply to motion through space.
【Speed】 (see also HASTE ) denotes rate of motion, a value computable by dividing the distance covered by the time taken.
【Velocity】 denotes the 【speed】 of something that is directed along a given path. Ordinarily 【velocity】 suggests rate of motion in a straight line (linear 【velocity】 ) or in an arc or circle (angular 【velocity】 ).
【Momentum】 in general or casual use may take the place of 【speed】 or 【velocity】 , but in technical use it denotes not rate of motion but quantity of motion, a value determinable by multiplying the mass of a moving body by its 【velocity】 .
【Impetus】 (see also STIMULUS ) is a popular rather than technical synonym of 【momentum】 . In practice it is a closer synonym of impulse in the sense of the effect of an impelling force, for it regularly carries an implication of a rushing upon or an onset, with the result that it usually suggests great 【momentum】 or implies a powerful driving force as the cause of such 【momentum】 .
【Pace】 belongs here not as a technical term but as a term in general use to denote the 【speed】 of or as if of one (as a person or horse) going afoot.
【Pace】 often finds extended use in describing such things as activities, progress, or rate of production.
【Headway】 basically applies to motion forward and in this sense is used chiefly in reference to ships. However it frequently denotes rate of movement ahead and then is used in reference not only to ships but to whatever is capable of advancing or making progress.
