I've got a U-tube filled with Mercury and water. If I add 11.2 cm of water to the left side, how much does the mercury rise on the right side? For simplicity's sake, D will stand for density, p0 for initial pressure, w = water, m = mercury, h = 11.2 cm for the water and d = the distance the mercury rises, and g is gravity. The equation I think I'm supposed to use is p0 + Dw(g)(1/2 * h) = p0 + Dm(g)(d) --> Dw(1/2 * h) = Dm(d) d = [ Dw(1/2 * h) ] / Dm = [ 1,000 kg/m^3 ( 1/2 * 11.2 cm ) ] / 13.6*10^3 kg/m^3 d = .412 cm which is what the book says, but my question is why did I use (1/2 * h) instead of h? Is there another way to do this problem?