Q. A rectangular plate $2m \times 3m$ is immersed in water in such a way that its greatest and least depth are 6m and 4m respectively from the water surface. The total thrust on the plate is
A) $294 \times 10^{3}$ N
B) 294 N
C) $100 \times 10^{3}$ N
D) $400 \times 10^{3}$ N
Explanation
(a) Given size of the plate $= 2m \times 5m$ and
Greatest and least depths of the plate are 6m and 4m
We know that area of the plate $A = 2 \times 3 = 6m^{2}$
And depth of centre of the plate
$x^{-} = \frac{6 + 4}{2} = 5\ m$
$\therefore$ Total thrust on the plate
$\rho = \rho_{w}g\ {\overrightarrow{A}}_{x}$
$= 10^{3} \times 9.8 \times 6 \times 5$
$= 294 \times 10^{3}$ N
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.