Horizontal acceleration due to earthquake results in A. hydrodynamic pressure B. inertia force into the body of the dam C. both (A) and (B) D. none of the above

The correct answer is C. both (A) and (B).

When an earthquake occurs, the ground moves horizontally. This horizontal movement causes the water in a reservoir to move as well. The movement of the water creates a hydrodynamic pressure on the dam. The hydrodynamic pressure can cause the dam to vibrate and can also cause the dam to move horizontally.

The horizontal acceleration of the ground also causes the inertia

force into the body of the dam. The inertia force is the force that resists the motion of the dam. The inertia force can cause the dam to bend and can also cause the dam to crack.

Both the hydrodynamic pressure and

the inertia force can cause the dam to fail. Therefore, the correct answer is C. both (A) and (B).

Here is a more detailed explanation of each option:

• Option A: Hydrodynamic pressure. When an earthquake occurs, the ground moves horizontally. This horizontal movement causes the water in a reservoir to move as well. The movement of the water creates a hydrodynamic pressure on the dam. The hydrodynamic pressure can cause the dam to vibrate and can also cause the dam to move horizontally.

• Option B: Inertia force into the body of the dam. The horizontal acceleration of the ground also causes the inertia force into the body of the dam. The inertia force is the force that resists the motion of the dam. The inertia force can cause the dam to bend and can also cause the dam to crack.

• Option C: Both (A) and (B). Both the hydrodynamic pressure and the inertia force can cause the dam to fail. Therefore, the correct answer is C. both (A) and (B).