An unbalanced force is a force that, when resolved into vector components, will not cancel out, creating some net force (or a force component) on the object. Hence, when an unbalanced force is applied to an object, Newton's laws of motion are applicable. According to the first law, the applied force will likely change the state of the motion of the object. If the object was at rest, it may cause it to move (provided sufficient force is applied). If the object was in motion, the force may aid or inhibit the motion or change the direction of the object. The acceleration of the body, as a result of this unbalanced force, can be calculated using the second law of motion. 

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