Question

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

Answer 1

you can't tell if you don't know the height of carton. . .
else for the start initial velocity will be high as the level of will come down the velocity will decrease. . .
in case carton is air tight then small hole would not be enough to leak milk out of carton because there should be another hole so that air take place of milk leaked out. . .

Answer 2

Why don't you elaborate on you question a little bit, @chelsae?

Answer 3

while using bernoulli's equation we cancel out the atmospheric pressure on both the sides because it is considered to be constant over the surface of the container.
hope that was your doubt...