Answer::
a) 1,231,504 N b) 318,322 N. c) 493.33 kPa.
Explanation:
a) We can calculate the weight of a cylindrical colum of water, as follows:
Fg = δH2O * V * g = δH2O * π* r2 * h * g = 1,000 kg/m3*π*(1.00)2 m2 *40.0 m* 9.8 m/s2
Fg = 1,231,504 N.
b) In order to get the force exerted by air on a disk at the water´s surface, we can apply the definition of pressure, and use the value for atmospheric pressure, as follows:
Fa = Pa.A = 101.325 k N/m2 * π* r2 = 101.325 kN/m2 * π * (1.00) m2
Fa = 318,322 N
c) At a depth of 40.0 m, the absolute pressure supported by the water column is the sum of the atmospheric pressure, plus the pressure created by the weight of the water column, as follows:
p = po + δH2O * g * h
p= 101.325 kN/m2 + 1,000 kg/m3 * 9.8 m/s2 * 40.0 m = 101,325 N/m2 + 392,000 N/m2
p= 493,325 N/m2 = 493.33 kPa.