If block A moves downwards at a velocity of 5 ft/s while the cords is
free to move on the pulley. Determine the velocity of block B, assume
that the mass of the cord is negligible.

1) 5 ft/s
2) 6 ft/s
3) 4 ft/s
4) 4.5 ft/s

Let S_{A} be the distance of the block A from the datum line
and S_{B} be the distance of the block B from the datum line.
So the total lenght of the cord L, L = S_{A} + L_{CD}
+ S_{B}, differentiating with respect to time we have V_{A}
+ V_{B} = 0, V_{B} = -V_{A} = -5 ft/s