The correct option is **B. 0°**. ### Detailed Explanation: When two forces act on an object, the resultant force is the vector sum of those two forces. The angle between the two forces plays a crucial role in determining the magnitude of the resultant force. 1. **Understanding Resultant Force**: - The resultant force \( R \) can be calculated using the formula: \[ R = \sqrt{F_1^2 + F_2^2 + 2F_1F_2 \cos(\theta)} \] where: - \( F_1 \) and \( F_2 \) are the magnitudes of the two forces, - \( \theta \) is the angle between the two forces. 2. **Analyzing the Angle**: - When the angle \( \theta = 0° \), the forces are acting in the same direction. The formula simplifies to: \[ R = F_1 + F_2 \] This is the maximum possible resultant because both forces add directly. 3. **Other Angles**: - If \( \theta = 90° \), the forces are perpendicular to each other. The resultant is given by: \[ R = \sqrt{F_1^2 + F_2^2} \] This is less than the sum of the forces when they are aligned (0°). - If \( \theta = 180° \), the forces are acting in opposite directions. The resultant is: \[ R = |F_1 - F_2| \] This can be zero if the forces are equal, or it will be less than the sum of the forces when they are not equal. - If \( \theta = 45° \), the resultant is: \[ R = \sqrt{F_1^2 + F_2^2 + 2F_1F_2 \cos(45°)} \] This is also less than the maximum resultant at 0°. ### Why Other Options Are Incorrect: - **A. 45°**: - At this angle, the forces are neither fully aligned nor fully perpendicular. The resultant is less than the maximum possible value, which occurs at 0°. - **C. 90°**: - The forces are perpendicular, leading to a resultant that is less than the sum of the two forces. This is a common scenario in physics, but it does not yield the maximum resultant. - **D. 180°**: - The forces are in opposite directions, which can lead to cancellation if they are equal, resulting in a minimum resultant. This is the least favorable angle for maximizing the resultant. ### Summary of Key Points: - The maximum resultant of two forces occurs when they are aligned (0°). - The formula for the resultant incorporates the cosine of the angle between the forces. - Perpendicular forces (90°) and opposite forces (180°) yield lower resultant magnitudes. - Understanding the vector nature of forces is crucial for solving problems related to resultant forces. This understanding is essential for solving problems in physics related to forces and their interactions.