Question

A square plate of side $30\text{m}$ is placed at $1\text{m}$ below the surface of water. The atmospheric pressure is $1.013\times {10}^5{\text{N m}}^{-2}$. Calculate the total thrust on the plate. (Given: Density of water = ${10}^3{\text{kg m}}^{-3},g=10{\text{m s}}^{-2})$

• A. $2.22\times {10}^7\text{N}$
• B. $3.33\times {10}^7\text{N}$
• C. $9.99\times {10}^7\text{N}$
• D. $1.11\times {10}^7\text{N}$

Answer 1

The correct option is C $9.99\times {10}^7\text{N}$

Total thrust = Total pressure $\times$ Area of plate
Total thrust $=(P_0+\rho gh)\times (30\times 30)$
Total thrust $=(1.013\times {10}^5+{10}^3\times 10\times 1)\times (30\times 30)$
Total thrust $=(1.11\times {10}^5)\times \left(900\right)$
Total thrust $=9.99\times {10}^7\text{N}$