The law of acceleration states that an object's motion will remain constant unless?

The law of acceleration, derived from Newton's Second Law of Motion, asserts that an object's motion will remain unchanged unless acted upon by an external force. This principle emphasizes the relationship between force, mass, and acceleration; specifically, that a net force is required to change an object's state of motion. If no force is applied, an object will either remain at rest or continue to move in a straight line at a constant velocity, illustrating the concept of inertia.

The notion of gaining weight does not intrinsically alter the motion of an object; it simply changes the mass without an external force acting on it. Similarly, being at rest or a change in surface condition does not inherently necessitate a change in motion unless an external force is applied. Thus, the correct understanding hinges on the presence of an external force, which is the condition that activates a change in motion according to the law of acceleration.