Hey, One of my homework tasks is, embarrasing, too hard for me to tackle without some help. So I help somebody can help me with the following problem: TASK: "You have a filled glass of water. A straw is stuck partly down into the glass (a depth d from the surface), the other end of the straw is on the outside (a distance h below the surface). The surface of the water is at a height y1. The glass' cross section area is A1, and the straw's cross section area is A2. We assume that A1 is much larger than A2, and that there goes a "flow line" from the water surface until the end (the one with the distance h from the surface) of the straw." Illustration: http://www.student.dtu.dk/~s052861/fysikprob.jpg [Broken] a) Decide the velocity of the water, that flows out ouf the straw, when the glass is filled (the surface of the water is at y1. b) Show, that the height y of the water, can be expressed by this equation: dy/dt = - A2/A1 * sqrt(2 * g * (y - y2)). c) How long will it go until the water stops flowing out of the straw? So, my problem is that I really don't now where to start. I've tried to think out a way to apply Bernoullis equation, or to calculate the pressure at the entrance of the straw and using that in some way... But I really need a hint about what I should focus on!