Given below are two statements:
**Statement I:** When the speed of a liquid is zero everywhere, the pressure difference between any two points depends on the equation $P_1 - P_2 = \rho g(h_2 - h_1)$.
**Statement II:** In the venturi tube shown, $2gh = v_1^2 - v_2^2$.
In the light of the above statements, choose the most appropriate answer from the options given below.
Answer: (B) Statement I is correct but Statement II is incorrect.
**Statement I:** For a liquid at rest, $P + \rho gh$ is the same everywhere, so $P_1 - P_2 = \rho g(h_2 - h_1)$. Correct.
**Statement II:** Bernoulli's equation along the horizontal tube:
$$P_1 + \frac12\rho v_1^2 = P_2 + \frac12\rho v_2^2 \Rightarrow P_1 - P_2 = \frac12\rho(v_2^2 - v_1^2)$$
With $P_1 - P_2 = \rho gh$: $2gh = v_2^2 - v_1^2$, not $v_1^2 - v_2^2$. Incorrect.
Solution by Sreeraj P, M.Sc Physics