Which law of motion states that a body continues in its state of rest or uniform motion in a straight line unless an unbalanced force acts on it?

The statement describes Newton's First Law of Motion. This law, also known as the law of inertia, asserts that an object will remain at rest or continue to move in a straight line at a constant speed unless acted upon by an external, unbalanced force. This principle illustrates the concept of inertia, where an object maintains its current state of motion unless disrupted by an external force.

In practical applications related to water and fuel systems maintenance, understanding this principle is crucial. For instance, when analyzing the behavior of fluids in pipes or tanks, recognizing how fluids continue to flow (or remain stagnant) under various forces can be vital for proper system maintenance and troubleshooting.

The other options refer to different aspects of motion: the Second Law relates force, mass, and acceleration (F=ma), and the Third Law states that for every action, there is an equal and opposite reaction. However, they do not address the concept of inertia or the condition of an object remaining in its current state until affected by an unbalanced force, making the First Law the only applicable answer to this question.