Blocks shown in figure have been placed on a smooth horizontal surface and mass of `(n + 1)^(th)` block is `(1)/(20)` times the mass of `n^(th)` block (where `n=1,2,3,4,….`). The first block is given an initial velocity `u` towards the second block. All collision are head on elastic collisions. If `u = 10 m//s` then how many blocks must be kept so that the last one acquires speed equal to or greater than the escape speed `(=11.0 km s^(-1))`
[Take `log_(10)((40)/(21))=0.28 and log_(10)(11)=1.04`]

Answer

12