Well wiki say that: Dreadnought cut the submarine in two after a short chase. So I think they want to ram it.
Oh,
Dreadnought did
intend to ram the sub.
The fact is that she wasn't
actively hunting the submarine; the sub lost depth control after not compensating for a torpedo launch.
Dreadnought was simply looking the right direction at the right time, and the sub magically appeared just off her bow. An
accident caused by a diving officer's mistake caused the sub to broach, and
Dreadnought took advantage of her high speed to catch the sub and ram her.
Succesfull as it was in that instance, it still sounds a bit like the proverbial "Taking a sledgehammer to kill a mosquito" concept.
That is one truism about warfare, though, that rarely disappoints, and that is "Always expect the unusual in war".
(That is in third place behind "Never get involved in a land war in Asia" and "Never match wits with a Sicilian when death is on the line".)