推荐回答（5个）
马赫是速度单位，公里是长度单位，无法对等比较。
马赫的大约速度换算一般认为相当于340.3 m/s，又大约等同于1225 km/h，761.2 mph，或者1116 ft/s。即视为等于声音在15摄氏度（59华氏度，288.15开氏度）的空气中传播的速度。
马赫数1即一倍音速。马赫数小于1者为亚音速，马赫数大于5左右为超高音速。马赫数是飞行的速度和当时飞行的音速之比值，大于1表示比音速快，同理，小于1是比音速慢。
扩展资料
马赫一般用于飞机、火箭等航空航天飞行器。由于声音在空气中的传播速度随着不同的条件而不同，因此马赫也只是一个相对的单位，每“一马赫”的具体速度并不固定。
在低温下声音的传播速度低些，一马赫对应的具体速度也就低一些。因此相对来说，在高空比在低空更容易达到较高的马赫数(摄氏零度之海平面音速约为 1193 km/hr；一万公尺高空的音速约为 1062 km/hr)。
当马赫数Ma<0.3时，流体所受的压力不足以压缩流体，仅会造成流体的流动。在此状况下，流体密度不会随压力而改变，此种流场称为亚音速流（Subsonic
flow），流场可视为不可压缩流场。一般的水流及大气中空气的流动，譬如湍急的河流、台风风场和汽车的运动等，皆属于不可压缩流场。
当马赫数Ma>1.0，称为超音速流（Supersonic
flow），此类流况在航空动力学中才会遇到。现在中国已经成功研制出并成功试飞超高音速飞机，最高可达6倍音速。
参考资料来源：百度百科-马赫
马赫不是距离单位，而是速度单位。
马赫：物体速度与音速之比值，即音速之倍数。以奥地利物理学家马赫（1838-1916）为名。
音波可以在固体、液体或是气体介质中传播，介质密度愈大，则音速愈快。在空气中，音速又会依空气之状态（如湿度、温度、密度）不同而有不同数值。如摄氏零度之海平面音速约为 1193 km/hr；一万公尺高空之音速约为 1062 km/hr。
一般声速为340米每秒，换算后=1224千米每小时。
当然，声速标准的不同会导致一马赫所代表的速度不同
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