A stretching force of 100 N is applied at one end of a spring balance and an equal stretchign force is applied at the other end at the same time. The reading on the balance will be

Options

A. 200 N
B. 100N
C. 400N
D. zero

Explanation

To solve the problem, we need to analyze the forces acting on the spring balance when equal stretching forces are applied at both ends.

### Step-by-Step Solution:

1. **Understanding the Setup**:
- We have a spring balance with a stretching force of 100 N applied at one end and an equal stretching force of 100 N applied at the other end simultaneously.

2. **Identifying Forces**:
- The first force (F1) is 100 N acting downwards on one end of the spring balance.
- The second force (F2) is also 100 N, but it acts upwards on the other end of the spring balance.

3. **Analyzing the Forces**:
- The spring balance measures the force exerted on it. In this case, both forces are equal and opposite.
- The downward force (100 N) and the upward force (100 N) will create a tension in the spring.

4. **Applying Newton's Third Law**:
- According to Newton's Third Law of Motion, for every action, there is an equal and opposite reaction.
- Therefore, the spring will exert an upward force equal to the downward force applied.

5. **Calculating the Reading on the Spring Balance**:
- Since both forces are equal (100 N downwards and 100 N upwards), they will balance each other out.
- The reading on the spring balance will reflect the force applied, which is 100 N.

6. **Conclusion**:
- The reading on the spring balance will be **100 N**.

### Final Answer:
The reading on the spring balance will be **100 N**.