Fluid Statics MCQ with answer and solution

Concept

When liquid pushes a vertical wall from both sides, the net pressure acting on the wall is the difference between the two opposing pressures because they act in opposite directions.

Formula

P_net = P₁ - P₂

Step-by-step solution

1. Understand that liquid pressure acts perpendicular to the submerged vertical wall on both sides. 2. Let the pressure from the first liquid side be P₁ and from the other side be P₂. 3. Since both pressures push in opposite directions against each other, the net or resultant pressure is found by subtracting the smaller pressure from the larger one. 4. Therefore, the resultant pressure is the difference of the two pressures. Answer: (B) Difference

Explanation

Liquid pressure pushes outwards in all directions. When a wall has liquid on both sides, the pressures push against each other. The net force or pressure is the difference between the two opposing forces.

Why the other options are wrong

A: Sum is wrong because opposing pressures subtract, not add. C: Arithmetic Mean is wrong because pressures do not average out. D: Geometric Mean is wrong because pressures combine algebraically, not geometrically.

Shortcut

Opposing forces always subtract each other to find the net effect.

Common mistake

Adding both pressures together, forgetting that they act in opposite directions.