Understanding the derivation the formulae will help you in solving problems even better. So, i suggest you to look into it.
Even though SHM and virtula work does not carry lot of weightage you need to be thorough in those topics also. Follow arihant and solve some problems in it.You will definitely feel confident.
I think maths might be a little difficult this time since IIT-K is preparing.But you need to get your right at the end of the day.If you do that half the job is done
all the best !!!