In a beam balance, when the beam is balanced in horizontal position, it is in __________ equilibrium.

Options

A. static
B. kinetic
C. balance
D. unbalance

Answer

To solve the question, we need to understand the concept of equilibrium in the context of a beam balance.

### Step-by-Step Solution:

1. **Understanding Beam Balance**: A beam balance consists of a horizontal beam that is supported at its center. When weights are placed on either side of the beam, the beam will tilt towards the side with the heavier weight.

2. **Condition for Balance**: For the beam to be balanced in a horizontal position, the torques (moments) produced by the weights on either side must be equal. This means that the forces acting on the beam must be balanced.

3. **Types of Equilibrium**: There are two main types of equilibrium:
- **Static Equilibrium**: This occurs when an object is at rest, and the sum of all forces and torques acting on it is zero.
- **Dynamic Equilibrium**: This occurs when an object is moving at a constant velocity, and the sum of all forces acting on it is also zero.

4. **Applying the Concept**: In the case of the beam balance, when it is perfectly horizontal and not moving, it indicates that the forces and torques are balanced. Therefore, the beam is not in motion and remains at rest.

5. **Conclusion**: Since the beam is at rest in the horizontal position, it is in **static equilibrium**.

### Final Answer:
In a beam balance, when the beam is balanced in horizontal position, it is in **static equilibrium**.

---