Thanks for the question. 

All three major subjects viz. Physics, Chemistry and Biology carry equal weightage in AIIMS MBBS exam, with 60 questions asked from each subject.

Significant portion of Reason-Assertion based questions. It is essential to have a firm command over the concepts to solve these questions.

 Gain an idea of the important topics for AIIMS MBBS 2018, you can do a subject-wise analysis from previous year papers. 

Physics will provide you with a good edge and is a sure shot winner. 

Check out our article... 

https://medicine.careers360.com/articles/how-prepare-for-aiims-mbbs-in-1-month

All the best...