Relative Equilibrium Solved Problems

Pressure problem:

a) Calculate the absolute pressure at an ocean depth of 1000 m. Assume that the density of water is 1000 kg/m³  and that P₀  = 1.01 x 10⁵ Pa (N/m²).

b) Calculate the total force exerted on the outside of a 30.0 cm diameter circular submarine window at this depth.

Solution:

(a)

(b)

Manometer problem:

A U-tube manometer in Fig. is used to measure the gage pressure of a fluid P of specific weight  = 800 kg/m³ . If the specific weight of the liquid Q is = 13.6×10³ kg/m³ , what will be the gage pressure at A if,

 a) h₁ = 0.5 m and D is 0.9 m above BC?                                              

 b) h₁ = 0.1 m and D is 0.2 m below BC?

Solution:

(a)

(b)

The negative sign indicating that P_A is below atmospheric pressure. The absolute pressure at A.