In the figure, what should be mass m so that block A slide up with a constant velocity?

Answer

1 sec

Explanation

`a_("rel")=2((4-1)/(4+1))hat(j)=12ms^(-2)`
`l= 6m`
`l=(1)/(2)a_("rel")t^(2)`
`6=(1)/(2)xx12xxt^(2)`
`t = 1s`