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Newton’s First Law Of Motion And Its Examples

Newton’s First Law of Motion, also known as the law of inertia, states that an object at rest will remain at rest, and an object in motion will remain in motion with a constant velocity unless acted upon by a net external force.

Newton's First Law Of Motion

What Are Newton’s 3 Laws?

Newton ‘s laws are three principles that serve to describe the movement of bodies, based on a system of inertial references (real forces with constant speed).

Newton’s three laws are:

  • First law or law of inertia.
  • Second law or fundamental law of dynamics.
  • Third law or principle of action and reaction.

These laws that relate the force, speed and movement of bodies are the basis of classical mechanics and physics. They were postulated by the English physicist and mathematician Isaac Newton in 1687.

Newton’s First Law:

Law Of Inertia:

The law of inertia or first law of Newton postulates that a body will remain at rest or in straight motion with a constant velocity unless an external force is applied.

In other words, it is not possible for a body to change its initial state (be it rest or motion) unless one or more forces intervene.

Newton’s first law FORMULA:

Fnet = 0 if velocity is constant

If the sum of the forces (Σ F) applied on a body is equal to zero, then the change in its speed with respect to time (dv/dt) will also be equal to zero.

An example of Newton’s first law is a ball at rest. In order for it to move, it requires a person to kick it (external force); otherwise it will remain at rest.

On the other hand, once the ball is in motion, ignoring friction with the ground, another force must also intervene so that it can stop and return to its state of rest.

Although this is the first of the laws of motion proposed by Newton, this principle had already been postulated by Galileo Galilei in the past. For this reason, Newton is only credited with publishing the law and Galilei is recognized as the original author.

Examples Of Newton’s First Law Of Motion:

Here are some examples to illustrate this law:

  1. Stationary Car: A car parked on the side of the road will remain stationary until a force (such as pushing it or the engine starting) is applied to set it in motion.
  2. Moving Soccer Ball: If you kick a soccer ball on a field with no friction or air resistance, it would continue to roll at a constant speed indefinitely. In reality, factors like friction and air resistance will eventually slow it down.
  3. Books on a Table: Books placed on a table will stay there until an external force (like a hand pushing them or the table collapsing) acts upon them.
  4. Ice Skater: An ice skater gliding across the ice will keep moving in a straight line at a constant speed unless an external force (such as friction from the ice or a push from another skater) changes their motion.
  5. Crumpled Paper Falling: If you crumple a piece of paper and drop it, it will fall straight down due to gravity, experiencing little horizontal motion. The vertical motion is influenced by gravity, while the horizontal motion is largely unaffected unless another force (like wind) acts on it.
  6. Spacecraft in Space: Objects in outer space, such as a spacecraft, will continue moving at a constant velocity unless influenced by gravitational forces or collisions with other objects.


in a real-world scenario, factors like friction, air resistance, and other external forces are usually present and can affect the motion of objects. However, Newton’s First Law provides a useful conceptual framework for understanding the basic principles of motion.


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