I wonder why the pressure at exit point is Patm(atmospheric pressure)! can you explain?? is it a general assumption applied to all similar type of questions?

Example 6 In the figure below, a pump forces water at a constant flow rate through a pipe whose cross-sectional area, A, gradually decreases: at the exit point, A has decreased to 1/3 its value at the beginning of the pipe. If y = 60 cm and the flow speed of the water just after it leaves the pump (Point 1 in the figure) is 1 m/s, what is the gauge pressure at Point 1? exit - A A Point 1 Pump sh= 0.6 m VI = 3 Im/s A. V. = Azz Solution. We'll apply Bernoulli's Equation to Point 1 and the exit point, Point 2. We'll choose the level of Point 1 as the horizontal reference level; this makes y, = 0. Now, because the cross-sectional area of the pipe decreases by a factor of 3 between Points 1 and 2, the Continuity Equation tells us that the flow speed must increase by a factor of 3; that is, v2 = 301. Since the pressure at Point 2 is Porn Bernoulli's Equation becomes p. + levit egg, = Pi + 2 pu, = Pam + P&/2 + 2 puz Now, P, is the total pressure at Point 1. Recall that gauge pressure is Plot - Patm) SO P gauge= P - Pacm' Therefore, P - Pam = P8/2 + 2 puz - E pup = P8 2 + 2 P (30, )2 - 2 pu, = P(872 + 40,) = (1,000 kg/m') [(10 m/s?) (0.6 m) + 4(1 m/s)' ] = 10' Pa