When a pair of balanced forces acts on a body, the _______ force acting on it becomes zero.

Options

A. gravitational force
B. resultant force
C. electrostatic force
D. contact force

Answer

To solve the question, "When a pair of balanced forces acts on a body, the _______ force acting on it becomes zero," we need to understand the concept of balanced forces and resultant forces.

### Step-by-Step Solution:

1. **Understanding Balanced Forces**:
- Balanced forces are two or more forces acting on an object that are equal in size but opposite in direction. When balanced forces act on an object, they do not cause the object to move.

2. **Identifying the Forces**:
- Let's denote the two balanced forces as \( F_A \) and \( F_B \). For example, if \( F_A = 5N \) acting to the right and \( F_B = 5N \) acting to the left, these forces are balanced.

3. **Calculating the Resultant Force**:
- The resultant force is the vector sum of all the forces acting on an object. In the case of balanced forces:
\[ \text{Resultant Force} = F_A + F_B \]
- Since \( F_A \) and \( F_B \) are equal in magnitude but opposite in direction, we can represent this mathematically as:
\[ \text{Resultant Force} = 5N + (-5N) = 0N \]

4. **Conclusion**:
- When a pair of balanced forces acts on a body, the resultant force acting on it becomes zero. Therefore, the correct answer to fill in the blank is "resultant".

### Final Answer:
When a pair of balanced forces acts on a body, the **resultant** force acting on it becomes zero.

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