Which fundamental law forms the basis of Bernoulli's equation?

$A$ tank of height $15 \ m$ and cross-section area $10 \ m^2$ is filled with water. There is a small hole of cross-section area $a$ which is much smaller than the container, located at a height of $12 \ m$ from the base of the container. How much force should be applied with a piston at the top level, so that the water coming out of the hole hits the ground at a distance of $16 \ m$ (in $kN$)? (Take, density of water $\rho = 1000 \ kg \ m^{-3}$ and $g = 10 \ m/s^2$)

$A$ fully loaded Boeing aircraft has a mass of $5.4 \times 10^5 \, kg$. Its total wing area is $500 \, m^2$. It is in level flight with a speed of $1080 \, km/h$. If the density of air $\rho$ is $1.2 \, kg/m^3$,the fractional increase in the speed of the air on the upper surface of the wing relative to the lower surface in percentage will be $(g = 10 \, m/s^2)$.

$A$ wind with speed $40 \ m/s$ blows parallel to the roof of a house. The area of the roof is $250 \ m^2$. Assuming that the pressure inside the house is atmospheric pressure,the force exerted by the wind on the roof and the direction of the force will be $(\rho_{air} = 1.2 \ kg/m^3)$.

$A$ fully loaded Boeing aircraft has a mass of $3.3 \times 10^5 \text{ kg}$. Its total wing area is $500 \text{ m}^2$. It is in level flight with a speed of $960 \text{ km/h}$. Estimate the pressure difference between the lower and upper surfaces of the wings.

Is Bernoulli's equation unsteady? Explain.