Block A has a constant velocity of 48 in./s to the left. For the position shown, determine the velocity of block B. (Note: The radius of the pulley may be neglected.) Solution For the triangle of sides 2ft and 1.5 ft : let 2ft side = x (variable ) let 1.5ft side = c constant through out the motion. Hypotenuse : s^2 = c^2 + x^2 also a variable differentiate wrt t s*ds/dt = x*dx/dt dx/dt = 48in/s at x = 2ft and s = 2.5ft ds/dt = 38.4ft/s Since string is inextensible ds/dt will be same as the velocity of block B .