Doubt from newton's laws of motion

solved
hard
newtons-law-of-motion
pulley-system
find-friction
pp
#1

how we can solve it by using taking it as system (how to right equation for it) doubt is when we can take them system..
20190907_233129

@Tanmay_1 sir @Viram_2019 sir @Abhishek_2021_2..

#4

#5

@Tanmay_1 sir not asking i know this solution my doubt is when i can take it system..
fnet=0
how to right equation of fnet so that friction becone internal force..

Doubt from centre of mass
#6

Ok i study your point then try ...

#7

@arush_2019 or @Mayank_2019_1 sir @Priya_1 mam please see the doubt