Astronomy Practice Exam

What does Newton's first law of motion state?

1. An object will only move if a force acts upon it.

2. An object moves at constant velocity unless a net force acts to change its speed or direction.

3. All motion requires a continuous application of force.

4. Static objects are in motion until a force is applied.

The correct answer is: An object moves at constant velocity unless a net force acts to change its speed or direction.

Newton's first law of motion, often referred to as the law of inertia, establishes the principle that if no net force acts on an object, it will maintain its current state of motion. This means that an object at rest will remain at rest, and an object in motion will continue to move at a constant velocity in a straight line. This foundational concept highlights that changes in motion—either acceleration or deceleration—only occur as a result of an applied force. By asserting that an object will only change its state of motion when a net force is applied, this law underscores the inherent resistance of matter to changes in motion. The understanding of this law is essential in explaining a wide range of physical phenomena, from why passengers lurch forward in a car when it suddenly stops, to the motion of celestial bodies in space, which continue on their paths unless acted upon by gravitational forces. This characteristic of inertia is pivotal in classical mechanics and sets the stage for the other laws of motion, linking directly to concepts of equilibrium and dynamics. In this context, one can appreciate why the other options do not reflect the accurate phrasing or implications of Newton's first law, as they either suggest misunderstandings about the conditions under which movement occurs or interpret activity as requiring continuous