Hello aspirant .

Minimum marks to score in qualifying examination is 50% marks(All subjects are to be passed ) in aggregate and also in PCM. If you score above 50% , you are eligible for B.arch.

As you told that you have failed in physics in 2nd puc exam , you are not eligible to do B.arch course.


For more information on eligibility refer 

https://www.google.com/amp/s/engineering.careers360.com/articles/nata-eligibility-criteria/amp

All the best.

For doing b. Arch course you need at least 50% in 10+2. If you're meeting with the criteria then wish you luck!