a. A steady stream of liquid flowing through a pipe of variable cross-section presses the section of pipe A between sections 1 and 2, which according to Newton's third law presses the liquid in the opposite direction. Consequently, the force acting on the liquid from this section is directed against the motion of the liquid. Why does the fluid in the region to the right of section 2 have more velocity than in the region to the left of section 1? b. What is the force acting on the liquid on the side of the pipe section A? The area of sections 1 and 2 is equal to S1 and S2, respectively. The density of the liquid is ρ. In the region to the right of section 2 the velocity of the fluid is v and the pressure in it is zero.