>>1676532i don't know the correct scientific terminology. but, if you gave a man a spade at the start of the day and told him to dig a big hole, then at the end of the day, that hole represents 'one manpower'.
you could then more or less expect ten similar men to dig ten such holes in one day. likewise, a special hole-digging machine might dig five such holes in a day, so that machine has five manpower.