Laws of Motion and Linear Momentum

Newton's First Law of Motion

Newton's First Law of Motion is a fundamental principle of physics that describes the behavior of objects in the absence of external influences. It state that an object continues in its current state of rest or in its state of uniform motion while moving in a straight line until and unless an external force is applied to it. This law implies that an object will not change its motion—meaning it will not start moving, stop moving, or change direction—without the intervention of an outside force. This concept is closely associated with the property of inertia, which is the inherent tendency of all matter to resist changes in its state of motion.

Linear Momentum

Linear momentum is a quantitative measure of an object's motion that takes into account both its size and its speed. It is formally defined as the product of the mass and the velocity of an object. In physics and engineering, this quantity is represented by the symbol $p$. Because it is the product of mass (a scalar) and velocity (a vector), linear momentum is itself a vector quantity. This means that to fully describe the momentum of an object, one must specify both its magnitude and the direction in which the object is moving.

The mathematical formula used to calculate linear momentum is:

$p = m \times v$

In this equation, $m$ stands for the mass of the object and $v$ stands for its velocity. The SI unit for linear momentum is derived from the units of its components, resulting in kilogram-meter per second, which is written as $kg\,m/s$.

Newton's Second Law of Motion

Newton's Second Law of Motion expands upon the relationship between force, mass, and motion. It provides a formal statement regarding how much the motion of an object changes when a force is applied. It states that the rate of change of linear momentum of an object is directly proportional to the resultant force applied to that object. Furthermore, this change in momentum occurs specifically in the direction of the applied force. This law allows for the calculation of force based on how quickly the momentum of an object increases or decreases over a specific period of time.