Physics - Fluid Question with Solution | TestHub

By the equation of continuity, $A_1{v}_1=A_2{v}_2$.

Here, $A_1=750{\text{ cm}}^2$, $A_2=500{\text{ mm}}^2=5{\text{ cm}}^2$, and $v_2=30\text{ cm/s}$.

Substituting the values, $750\times v_1=5\times 30$.

$v_1=\frac{150}{750}=0.2\text{ cm/s}$.

Converting to m/s, $v_1=0.2\times 10^{-2}\text{ m/s}=2\times 10^{-3}\text{ m/s}$.

Since $v_1=\frac{dh}{dt}$, we have $\frac{dh}{dt}=2\times 10^{-3}\text{ m/s}$.

Comparing with $y\times 10^{-3}\text{ m/s}$, we get $y=2$.

Answer: $2$