Question

A boat travelling at $6m/s$ in sea water has a $250mm$ diameter propeller that discharges the water at a velocity of $12m/s$. Given that the density of seawater is $1030kg/m^3$. The effect of propeller hub is negligible. The magnitude of thrust produced $F$ is (in $N$)

• A. $1030$
• B. $2730$
• C. $4660$
• D. $980$

Answer 1

The correct option is B $2730$

Pressure difference across the propeller hubs
$=p_1-p_2=\frac{1}{2}\left(1030\right)({12}^2-6^2)$
$=55620p_a$
So,
the thrust produce=area x pressure difference

$=\pi \times {(125\times {10}^{-3})}^2\times 55620N$
$=2730.240N$
$\approx 2730N$