First law of motion

Newton's First law of motion

Newton's First Law of Motion: An object remains at rest or moves in a straight line at constant speed unless acted upon by an external force.

      If no external force is applied, a body at rest will stay at rest, and a body in motion will continue moving in a straight line at a constant speed. When an object moves with a constant speed and direction, it is said to have uniform velocity. And it's motion will be uniform. Newton's law gave us an idea about force and inertia.

What is a force?

    Force is an external agent that actually changes or tends to change the state of rest or of motion of a body. This idea actually obtained from Newton's first law of motion. Force does not always result in a change in the state of rest or motion of an object. Sometimes, it only tries to bring about a change. For example, if a person pushes against a wall, the wall doesn’t move, but a force is still being applied. In this case, the force attempts to change the state, but the state of rest remains unchanged.

Implications of Newton's First Law:

Understanding Newton's First Law of Motion and its implications is crucial for comprehending the behavior of objects and systems in the physical world. Let's explore some of the key implications of this law:

Inertia: It is an intrinsic property of a body by virtue of which a body tends to continue its state of rest or of motion.   

From Newton's first law of motion, it is clear that a body tends to continue its state of rest or of uniform motion. This state of rest or this state of motion can be changed by applying force. So everybody has a tendency to continue its old state. That tendency is called inertia.

 Inertia can be two types.
 i) inertia of rest
ii) inertia of motion

The tendency of a body to continue its state of rest is called inertia of rest. The tendency of a body to continue its state of motion is called inertia of motion. Inertia cannot be measured directly by some measuring device. Therefore inertia has no unit. Inertia is solely dependent on the mass of the object.
         Compared to a goat, an elephant has a much larger mass. It will be more inconvenient to remove an elephant than remove a goat.

Absence of External Forces:
The law emphasizes that objects only change their state of motion when external forces act upon them. This means that if an object is already in motion in a frictionless environment, it will continue moving indefinitely without any external force to oppose its motion. Likewise, if an object is at rest on a smooth surface, it will remain at rest until an external force is applied.

Equilibrium:
The concept of equilibrium is closely intertwined with Newton's First Law.  An object is said to be in equilibrium when the net force acting on it is zero, resulting in no changes in its state of motion. In simple terms, when the forces on an object are balanced, it stays at rest or moves with constant velocity. A common example is an object hanging from a string, where the tension in the string exactly counteracts the force of gravity.

Practical Applications:
Newton's First Law has numerous practical applications in everyday life and various fields of science and engineering. It helps explain the behavior of moving vehicles, the principles behind sports and games, the dynamics of space travel, and the design of safety features such as seat belts and airbags. By understanding this law, scientists