Figure shows two shells of masses `m_1` and `m_2` . The shells are concentric. At which point, a particle of mass m shall experience zero force?

Explanation

`Rate_(I) = k'_(1)[A][B] = 1 xx 10^(-5)(0.1)(0.1) = 1 xx 10^(-7) M s^(-1)`
`Rate_(II) = k_(1)[A] = 1 xx 10^(-4) xx 0.1`
`= 1 xx 10^(-5)Ms^(-1)`
(Its second step is fast and first step is slow as evident `k_(1)` and `k_(2)` values)
If rates are equal, then `k'_(1)[A][B] = k_(t)[A]`
`:. k'_(1)[A] = k_(t)`
`:. [B] = (k_(1))/(k'_(1)) = (1 xx 10^(-4)s^(-1))/(1 xx 10^(-5)M^(-1)s^(-1)) = 10 M`