Final answer:
Increasing the mass of the box would most likely require additional force to produce the same results.
Step-by-step explanation:
If a force of 5N is required to increase the speed of a box from 1.0 m/s to 3.0 m/s within five seconds along a level surface, the change that would most likely require additional force to produce the same results is increasing the mass of the box. Newton's second law of motion states that the acceleration of an object is directly proportional to the net force acting on it and inversely proportional to its mass. So, if the mass of the box is increased, a greater force would be needed to achieve the same acceleration.
For example, if the mass of the box is doubled, the force required to increase its speed from 1.0 m/s to 3.0 m/s would also need to be doubled. This is because the acceleration of the box is inversely proportional to its mass, so a greater force is needed to overcome the increased inertia.