International General Certificate of Secondary Education (IGCSE) Physics Practice Exam

When an unbalanced force acts on an object, that object experiences acceleration. This principle stems directly from Newton's second law, which states that the acceleration of an object is directly proportional to the net force acting on it and inversely proportional to its mass. This can be summarized in the equation: Force = mass × acceleration (F = ma).

When a net external force is applied to an object (meaning the forces acting on it are not balanced), the object will change its state of motion, leading to an increase in speed, a decrease in speed, or a change in direction, all of which are manifestations of acceleration. Therefore, the correct response highlights the relationship between unbalanced forces and the resulting acceleration of an object, emphasizing the effect that such forces have on its motion.