Question

(a) Calculate the absolute pressure at the bottom of a freshwater lake at a point whose depth is 28.4 m. Assume the density of the water is 1.00 103 kg/m3 and the air above is at a pressure of 101.3 kPa.

(b) What force is exerted by the water on the window of an underwater vehicle at this depth if the window is circular and has a diameter of 32.2 cm?

Answer 1

a) the absolute pressure at the bottom of a fresh-water lake = P=pressure of the above air + pressure of the above water
= 101.3 kPa + h *Rho*g
= 101.3*1000 Pa + 28.4* 1000 * 9.81Pa
= 380*1000 Pa = 380 KPa---answer

b) force exerted by the water on the window of an underwater vehicle at this depth if the window is circular and has a diameter of 32.2 cm

, so F = pA A = ?d²/4 = 3.14*(.322)^2/4 = 0.814 m²
= 380*0.814 = 30.92 kN ---answer

Hope it will help you.