"a hole is punched in a full milk carton, 10 cm below the top. what is the initial velocity of outflow? "

P 1 = 101,325 Pa (atmospheric pressure)
Milk has almost same density as water: (Rho)= 1,000 kg /m³ 
P 2 = 101,325 Pa + 1,000 kg/m³ · 9.81 m/s² · 0.1 m = 102,306 Pa
The hydrostatic equation:
P 1 + (Rho)v1² / 2 = P 2 + (Rho)·g·h2
101,325 + 1,000 v1²/2  = 102,306 + 1000 · 9.81 · 0.1
500 v 1² = 102,306 + 981 - 101,325
v 1² = 3.924
v 1 = √ 3.924
v 1 = 1.98 m/s
The initial velocity of outflow is 1.98 m/s.