Using constraint method find the relation between accelerations of `1` and `2`.

Explanation

At any instant of time Let `x_(1)` and `x_(2)` be the displancements of `1` and `2` from line (shown dotted). Here `x_(1)` and `x_(2)` are variables but,
or `x_(1)+ x_(2)=1` (length of string)
Differentiating with respect to time, we have
`v_(1) + v_(2) = 0` or `v_(1) = - v_(2)`
Again differentiating with respect to time, we get
`a_(1) + a_(2) = 0` or `a_(1) = -a_(2)`
This is the required relation between `a_(1)` and `a_(2)`, i.e. accelrations of `1` and `2` are equal but in opposite directions.