Final answer:
An unbalanced force causes an object at rest to accelerate, in accordance with Newton's first law of motion which states that a body at rest tends to stay at rest and a body in motion continues moving at a constant velocity unless acted upon by a net external force.
Step-by-step explanation:
Unbalanced forces change the motion of an object, meaning if an object is at rest, an unbalanced force causes the object to accelerate. This principle is encapsulated in Newton's first law of motion, which is also known as the law of inertia. According to this law, a body at rest remains at rest, and a body in motion remains in motion at a constant velocity unless acted upon by a net external force. This law demonstrates a deeper understanding of motion. A change in motion implies a change in velocity, which can be a change in speed, the direction of movement, or both. Therefore, an acceleration occurs when an unbalanced force acts on an object, altering its state of motion.