It's 'useless' trying to change her mind. = It's 'useless' to try to change her mind.
Drugs are 'useless' in treating the condition.
I made a 'useless' attempt at fixing the leak.
(..) Yeah? How about I make a point out of your pointy little head? Let me remind you, while my moral support is absolute, in a physical confrontation, I will be less than useless. There's not going to be a confrontation. In fact, I doubt if he can even spell "confrontation." C- O-N... frontation! (..)2007 TvShow: The Big Bang Theory Title: The Middle Earth Paradigm Season: 1 Episode 6