Walker, Halliday & Resnick — Fluids: Problem 11

11 The plastic tube in Fig. 14-27 has a cross-sectional area of $5.00 \text{ cm}^2$. The tube is filled with water until the short arm (of length $d = 0.800 \text{ m}$) is full. Then the short arm is sealed and more water is gradually poured into the long arm. When the total height of water in the long arm reaches $2.80 \text{ m}$, the seal is on the verging of popping. What force is then on the seal?