Ok, Air flows through this tube at a rate of 1200 cm^3/s. Assume that air is an ideal fluid. What is the height h of mercury in the right side of the U-tube? Here's a picture: http://session.masteringphysics.com/problemAsset/1001181/6/knight_Figure_15_64.jpg First, I found the velocity of the air in the 2 cm and 4 mm tube. In m/s, for the 2cm, i came up with 1200/(1000000pi(.01^2)) and for the 4mm 1200/(1000000pi(.002^2)) Then, I plugged it into bernoulli's equation, with the density of air as 1.2 kg/m^3. This gave the 2cm tunnel to have 5462.5 less pascals than the other 4 mm tube. Then, using 13540 for the kg/m^3 of Hg, and setting the pressures of the two sides equal, I came up with: 5462.5 = 13540 (9.8) (h), which gave me h= .0412 m, or 4.12 cm, which is wrong. Anybody know what I did wrong?