Depends how much you initially know about physics or not. But either way, you should definitely do it. In my opinion, first semester physics becomes pretty difficult half way through the semester, and it would be helpful if you had some previous knowledge about it, so you 'get' the nature of physics and the type of thinking involved in problem solving, so you'll be better prepared. Extension 1 maths had some very basic physics problems in it, which does help in the problem solving but still, I'd recommend you do the bridging course.