I'm a little confused about this equation v1A1=v2A2 , to solve for A i used pi*r^2 and then I solved for velocity 2 with all other variables known. This seemed pretty straight foward but i get a bad anwser. In the solutions for this problem they just took the diameters and squared it instead of taking the area of of a circle. Can some one please explain this to me, a copy of the problem is listed below. A 1.0-cm-diameter pipe widens to 2.0 , then narrows to 0.5. Liquid flows through the first segment at a speed of 4.0 m/s What is the speed in the second segment?