Answer: The only way for the object to change its motion is if an external unbalanced force acts on it.
Step-by-step explanation:
Newton's First Law of Motion (aka Law of Inertia) states:
An object at rest stays at rest and an object in motion stays in motion with the same speed and in the same direction unless acted upon by an unbalanced force.
Velocity is a VECTOR, so it has both magnitude (size) and direction. The magnitude of the velocity of an object in motion (its speed) can stay the same, but if it changes direction, its velocity has changed. The only way for the object to change its direction of motion is if an external unbalanced force acts on it.