What is the effect of an unbalanced force on an object?

An unbalanced force acting on an object leads to a change in the object's state of motion, specifically causing it to accelerate. According to Newton's second law of motion, the acceleration of an object is directly proportional to the net force acting on it and inversely proportional to its mass. This means that when there is a net force acting on an object that is not countered by another force of equal magnitude, the object will start to speed up, slow down, or change direction, depending on the direction of that net force.

For example, if a net force is applied to a stationary object, that force will cause the object to accelerate in the direction of the force. Similarly, if an object is already in motion and an unbalanced force acts upon it, that force will either speed it up, slow it down, or change its trajectory. Therefore, the correct answer highlights the fundamental concept of how forces influence an object's motion, aligning with the principles of dynamics in mechanics.