千米是指长度单位,俗称公里,英文用km(kilometre)表示。1790年5月由法国科学家组成的特别委员会,建议以通过巴黎的地球子午线所在经线圈全长的四万分之一作1千米=1000米=10000分米=100000厘米。
它将在300千米的高度绕地球运行。
带负电荷的区域非常大:数百米厚,直径达几千米。
The negatively charged region is large: several hundred meters thick and several kilometers in diameter.
卫星以11.2千米每秒的速度前进可以脱离地球引力,这被称为“逃逸速度”。
Eleven point two kilometers per second, at which satellites can be freed from the gravitation of the earth, is called "escape speed".
Sometimes they give you the speed in miles per hour, kilometers per year, pounds per square foot.
有时候速度的单位是英里/小时,千米/年,英磅/平方米
Soldiers were expected to be able travel thirty kilometers per day, in full pack.
士兵一天可以行进30千米,在全副装备的情况下。
They used even a horseback relay that could go a hundred kilometers a day.
采用了马背接力的形式,一日可以行进100千米。
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