Which statement best describes the difference between balanced and unbalanced forces acting on an object?

• A. Balanced forces always act in the same direction, while unbalanced forces act in opposite directions.
• B. Balanced forces result in $F=0$ and do not change the object's motion, while unbalanced forces result in $F\ne 0$ and cause the object to accelerate.
• C. Balanced forces only exist when an object is moving, while unbalanced forces only exist when an object is at rest.
• D. Balanced forces increase the speed of an object, while unbalanced forces decrease its speed.

Answer: (B)

Verified step by step guidance

1. Understand that forces are vectors, meaning they have both magnitude and direction, and multiple forces acting on an object combine to form a net force.
2. Recognize that balanced forces occur when the sum of all forces acting on an object equals zero, which can be written as \(\sum \vec{F} = 0\); this means there is no change in the object's motion.
3. Know that unbalanced forces occur when the sum of all forces acting on an object is not zero, written as \(\sum \vec{F} \neq 0\); this results in the object accelerating according to Newton's second law.
4. Recall Newton's second law of motion, which states that \(\sum \vec{F} = m \vec{a}\), where \(m\) is mass and \(\vec{a}\) is acceleration; if \(\sum \vec{F} = 0\), then \(\vec{a} = 0\) and the object’s velocity remains constant.
5. Conclude that balanced forces do not change the object's motion (it remains at rest or moves with constant velocity), while unbalanced forces cause a change in motion by producing acceleration.