Final answer:
A net force acting on an object changes its speed and direction of motion, thereby altering its position and displacement. The force leads to a change in momentum and causes an acceleration, which results in changes to the object's motion over time.
Step-by-step explanation:
When a net force acts on an object for some time, there are a few changes that can be observed in the object. Primarily, according to Newton's second law, a net force acting on an object is equal to the rate of change of the momentum of that object. This implies that if a net force is present, the object’s velocity and hence its speed and direction can change, resulting in an acceleration. Thus, a net force can change an object's speed.
Moreover, the position and displacement of an object will also change as a result of the net force acting over time. This is because the force affects the object's velocity, which in turn affects how it moves through space. If the force is consistent and in the same direction as the movement, displacement will increase linearly over time. However, if the force changes direction or magnitude, the resulting motion could involve changes in direction and could be more complex.