A block `A` of mass `m` is attached at one end of a light spring and the other end of the spring is connected to another block `B` of mass `2m` through a light string as shown in the figure. `A ` is held and `B` is in static equilibrium. Now `A` is released. The acceleration of `A` just after that instant is `a` . In the next case, `B` is held and `A` is in static equilibrium. Now when `B` is released, its acceleration immediately after the release is `b` . The value of `a//b` is (pulley, string and the spring are massless).

Options

A. 0
B. undefined
C. 2
D. `(1)/(2)`

Answer

C

Explanation

For first case tension in spring will be
`T_(s)=2mg` just after `'A'` is released.
`2mg-mg=ma` implies `a=g`
In second case `T_(s)=mg`
`2mg-mg=2mb `
`b=g//2`
`a//b=2` .