[amp_mcq option1=”9,000 kg” option2=”13,500 kg” option3=”18,000 kg” option4=”27,000 kg” correct=”option3″]
The correct answer is $\boxed{\text{D}}$.
The hydrostatic force on a surface is given by the following equation:
$$F = \rho g h A$$
where:
- $\rho$ is the density of the fluid,
- $g$ is the acceleration due to gravity,
- $h$ is the depth of the surface, and
- $A$ is the area of the surface.
In this case, we are given that the density of water is $\rho = 1000 \frac{kg}{m^3}$, the acceleration due to gravity is $g = 9.8 \frac{m}{s^2}$, the depth of the surface is $h = 3 m$, and the area of the surface is $A = 3 m \times 3 m = 9 m^2$. Substituting these values into the equation for the hydrostatic force, we get:
$$F = (1000 \frac{kg}{m^3})(9.8 \frac{m}{s^2})(3 m)(9 m^2) = 27,000 \text{ N}$$
Therefore, the hydrostatic force on the square surface is $\boxed{27,000 \text{ N}}$.
Option A is incorrect because it is the force on a square surface with an area of $1 m^2$. Option B is incorrect because it is the force on a square surface with an area of $2 m^2$. Option C is incorrect because it is the force on a square surface with an area of $4 m^2$.