Final answer:
When a balanced force is applied in the opposite direction, an object that is moving at a constant speed will change direction but continue moving at a constant speed.
Step-by-step explanation:
When an object is moving at a constant speed, it means that the forces acting on it are balanced. This means that the force in the opposite direction of motion is equal to the force in the direction of motion. If a balanced force is applied in the opposite direction the object is moving, it will cause the forces to become unbalanced.
When the forces are no longer balanced, the object will experience an acceleration in the opposite direction of its original motion. This will result in a change in its velocity, meaning that the object will change direction.
However, the object will not speed up or slow down, as the net force acting on it is still zero. Therefore, the object will continue moving at a constant speed, but in the opposite direction.
Learn more about the effect of a balanced force on an object's motion