The work done by the man was difficult.The man did the work

嗯,可以这么说……
其实The work done by the man was difficult可以变成从句形式：
The work which was done by the man was difficult.
（which was） done by the man是后置定语,修饰前面的the work,
字面上翻译是“被那个人做了的事情”,变为主动也就是“那个人做了事情”