Question

A horizontal water jet with a velocity of 10 m/s and cross-sectional area of 10 mm\(^2\) strikes a flat plate held normal to the flow direction. The density of water is 1000 kg/m\(^3\). The total force on the plate due to the jet is

• A. 100 N
• B. 10 N
• C. 1 N
• D. 0.1 N

Hint:

When dealing with jet propulsion and forces, remember to use the mass flow rate formula \( \dot{m} = \rho A V \) to calculate the force.

Answer 1

The Correct Option is A

The force exerted by a jet on a plate is given by \( F = \dot{m} \cdot V \), where \( \dot{m} \) is the mass flow rate and \( V \) is the velocity of the jet. The mass flow rate \( \dot{m} \) is given by: \[ \dot{m} = \rho A V \] Substituting the values for density \( \rho = 1000 \, \text{kg/m}^3 \), area \( A = 10 \times 10^{-6} \, \text{m}^2 \), and velocity \( V = 10 \, \text{m/s} \), the total force on the plate is 100 N. Hence, the correct answer is 100 N.