In the circuit element given here, if the potential at point `B = V_(B) = 0`, then the potentials of `A` and `D` are given as

Answer

`l`

Explanation

Velocity of mass`-1` when string is in normal length.
`v_(A) = sqrt(6gl - 2gl) = 2 sqrtgl`
Now impulsive tension acts on both bodies to come to common velocity Desplacement of C.M. when string becomes taut.
`Deltay_(1 cm) = (m xx l + m xx 0)/(m + m) = (l)/(2)`
Desplacment of CM masses reach the max. height
`Deltay_(2 cm) = (v_(2))/(2g) = (l)/(2) :. Deltay_(cm) = (l)/(2) + (l)/(2) = l`