Final answer:
Newton's second law states that an unbalanced force causes acceleration, which is directly proportional to the force and inversely proportional to mass.
Step-by-step explanation:
According to Newton's second law of motion, when an unbalanced force acts on a system, the object will be accelerated. The acceleration is directly proportional to the net external force acting on the system, in the same direction as the force, and inversely proportional to its mass. Therefore, the correct answers to fill in the blanks are 1) accelerated and 2) acceleration.