Determine the speed of block G, if the block Z is moving up with a velocity of 20 ft/s. The mass of the cord can be assumed negligible.
1) 15 ft/s
There is one cord in this system having segments which are changing length. Position coordinates SG and SZ will be used since each is measured from a fixed point (C or D) and extends along each block's path of motion. SZ is directed to point E since motion of Z and E is the same.
So the total length of the cord at any time is L = SG+ 3SZ,
neglecting the arc distance on the pulley because it remains constant.
So, the velocity of block G, VG = 20 ft/s (down)..