A fluid of density $\rho~$is flowing in a pipe of varying cross-sectional area as shown in the figure. Bernoulli's equation for the motion becomes:

1. $p+\dfrac12\rho v^2+\rho gh\text{=constant}$
2. $p+\dfrac12\rho v^2\text{=constant}$
3. $\dfrac12\rho v^2+\rho gh\text{=constant}$
4. $p+\rho gh\text{=constant}$

A wind with a speed of $40~\text{m/s}$ blows parallel to the roof of a house. The area of the roof is $250~\text{m}^2.$ 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:
$(\rho_{\text {air }}=1.2~\text{kg/m}^3)$
1. $4 \times 10^5~\text N,$ downwards
2. $4 \times 10^5~\text N,$ upwards
3. $2.4 \times 10^5~\text N,$ upwards
4. $2.4 \times 10^5~\text N,$ downwards

Water is flowing through a long horizontal tube. Let $P_A$ and $P_B$ be the pressures at two points $A$ and $B$ of the tube.