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

So, the upward velocity of B, V_B = 5 ft/s.