I always read in applications of integration is to figure out the arc length but they never tell us what is it good for I also couldn't find immediate results by using google, so can anyone tell me its uses?
OK, I'll give you a specific example. You are an engineer charged with building a suspension bridge. The cables are one of the most expensive parts of the bridge and you need to order them from the steel manufacturer. How long do they need to be? You need to give the manufacturer an accurate figure. If you get it wrong, you will probably get fired, and your career will be ruined. Using calculus, you can accurately calculate the length of the cables.
ok but then I think that it is more specialized knowledge ,so people who take calculus II don't need to learn it shouldn't they keep it for only math majors or civil engineering majors. I am saying that because I feel it is a pity that not being good in something understanding something won't be very useful to me affects my future.
What would you consider unspecialized knowledge? Writers don't need calculus at all, why teach it to everyone to begin with?!
Honestly it sounds like you're just finding an excuse for not liking it or not being very good at it.