A vertical rectangular wall with a width of 20 m and a height of 12 m is holding a 7-m-deep water body. The resultant hydrostatic force acting on this wall is (a) 1370 kN (b) 4807 kN (c) 8240 kN (d) 9740 kN (e) 11,670 kN

(c) 8240 kN

Resultant hydrostatic force F = 8240 kN

Explanation:

Force can be expressed as;

F = ma

F = mg 1

Where,

F = force

m = mass

a = acceleration

g = acceleration due to gravity

And we know that mass of an object is the product of

Density and Volume

m = pV

And volume V = area × height = Ah

m = pAh 2

Substituting m into equation 1

F = pAhg = pghA 3

Given;

Density of water p = 1000kg/m^3

g = 9.81m/s^2

Area A = 20m × 12m = 240m^2

h = depth/2 = 7/2 = 3.5m

Substituting the values into equation 3, we have;

F = 1000×9.81×3.5×240

F = 8240400 N

Resultant hydrostatic force F = 8240 kN