@Shwetanshu_2018 bro , @Viram_2019 sir please give analysis of question....

# Doubt from center of mass

If suppose S1 is dragged then the the cylinder (pipe) above and below it starts to roll, and there is pure rotation happening and for that the friction from S1 is enough i.e the lowermost pipe will roll without such that there is no friction acting on it from the ground .

Now , from this analysis it is clear that if S2 is dragged then only the layer below and above it will move and rest will be as it is , and hence when s2 it dragged then cylinders above S3 and below S1 will be stationary .

So for tower or collapse we just want that cylinder below S3 no more stays below it , so for that we need that the left most cylinder moves 2.5 cm i.e half of the gap between the pipes .

So we know in pure rolling if COM of cylinder moves X then it’s top most surface moves 2x so for com to move 2.5 cm the upper surface i.e the sheet should move 5 Cm