Newton's First Law of Motion, also known as the Law of Inertia, states that 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. This fundamental principle describes how objects behave when no net force is applied to them.
When we say an object at rest stays at rest, we mean that if something is not moving, it will continue to remain stationary unless a force acts upon it. For example, a book sitting on a table will stay there indefinitely. The book experiences gravity pulling it downward, but the table provides an equal and opposite support force upward. These balanced forces result in no net force, so the book remains at rest.
Newton's First Law of Motion, also known as the law of inertia, is one of the fundamental principles of physics. It states that an object at rest will remain at rest, and an object in motion will continue moving at constant velocity in a straight line, unless acted upon by a net external force. This law explains why a book sitting on a table doesn't spontaneously start moving.
The first part of Newton's First Law deals with objects at rest. An object at rest will remain at rest unless acted upon by a net external force. This principle explains why objects around us don't spontaneously start moving. A ball on the ground, a book on a shelf, or a car parked in a driveway will all remain stationary until something pushes or pulls them. This tendency to resist changes in motion is called inertia.
An object in motion stays in motion with the same speed and direction unless acted upon by a force. This means that if something is already moving, it will continue moving at constant velocity in a straight line forever, unless something interferes with it. A perfect example is a hockey puck sliding on smooth ice. With minimal friction, the puck glides in a straight line at nearly constant speed until it hits the boards or another object.
An unbalanced force is the key to changing an object's motion. When the total force acting on an object is not zero, we have an unbalanced force. This causes the object to accelerate, which means it can start moving, stop moving, speed up, slow down, or change direction. For example, when you push a box and the pushing force is greater than friction, there's a net unbalanced force that causes the box to accelerate forward.
Inertia is an object's resistance to changes in its state of motion. The more massive an object is, the more inertia it has. This means that heavier objects are harder to start moving when at rest, and harder to stop when in motion. For example, it takes much more force to push a heavy truck than to push a light bicycle. This relationship between mass and inertia is fundamental to understanding Newton's First Law and explains why massive objects resist changes in motion more than lighter ones.