Question

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

Answer 1

Answer:

(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