Assertion`:-` when two non parallel forces `F_(1)` and `F_(2)` act on a body. The magnitude of the resultant force acting on the is less than the `"sum"` of `F_(1)` and `F_(2)`
Reason`:-` In a triangle, any side is less then the `"sum"` of the other two sides.

Options

A. If both Assertion & Reason are True & the Reason is a correct explanation of the Assertion.
B. If both Assertion & Reason are True but Reason is not a correct explanation of the Assertiion.
C. If Assertion is True but the Reason is False.
D. If both Assertion & Reason are False

Explanation

To solve the question, we need to analyze the assertion and the reason provided.

### Step 1: Understanding the Assertion
The assertion states that when two non-parallel forces \( F_1 \) and \( F_2 \) act on a body, the magnitude of the resultant force \( R \) is less than the sum of the magnitudes of the two forces, i.e., \( R < F_1 + F_2 \).

### Step 2: Vector Addition of Forces
When two forces are acting at an angle (non-parallel), we can use the triangle law of vector addition to find the resultant. The magnitude of the resultant \( R \) can be calculated using the formula:
\[ R = \sqrt{F_1^2 + F_2^2 + 2F_1F_2 \cos \theta} \]
where \( \theta \) is the angle between the two forces.

### Step 3: Analyzing the Resultant
In the case of non-parallel forces, the angle \( \theta \) is not equal to 0° (which would make them parallel) or 180° (which would make them anti-parallel). Therefore, the cosine of the angle \( \cos \theta \) will be less than 1, leading to:
\[ R < F_1 + F_2 \]
This confirms the assertion.

### Step 4: Understanding the Reason
The reason states that in a triangle, any side is less than the sum of the other two sides. This is known as the triangle inequality theorem. In the context of vector addition, if we consider \( F_1 \) and \( F_2 \) as two sides of a triangle, the resultant \( R \) (the third side) must be less than the sum of the other two sides, which is \( F_1 + F_2 \).

### Step 5: Conclusion
Both the assertion and the reason are true. The assertion correctly describes the relationship between the resultant and the two forces, and the reason provides a valid explanation based on the triangle inequality theorem.

### Final Answer
- **Assertion**: True
- **Reason**: True
- **Conclusion**: Both the assertion and the reason are correct.