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If I don't show you any argument for v, it means v at time t and the subscript of 0 means t is 0. 如果我不對(duì)v做任何標(biāo)志,那就表示t時(shí)刻的速度v,下標(biāo)0表示的是t=0 耶魯公開(kāi)課 - 基礎(chǔ)物理課程節(jié)選