It’s no secret that constant motion defines our universe. Even in those seeming tranquil moments, we’re living on Earth—an astronomical entity that’s always on the go—spinning on its own axis and making its journey around the sun!
It will, however, be interesting to understand the concept of motion as defined in Physics. Let us start by understanding that the study of motion without regard to the forces or energies that may be involved is known as kinematics. It is the most superficial branch of mechanics. On an aside, the mechanics branch that deals with motion and forces is called dynamics.
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What is Motion? How do we define it?
When we talk about literal concepts, motion is defined as a change in the position of an object concerning time. So, whether it is water falling from a tap or the air we breathe, everything exhibits motion. Other day-to-day examples of motion include activities such as running, cycling, jumping, swimming, writing, typing, moving cars, throwing balls, and many more.
The motion of an object is described in terms of the following:
● Distance
● Displacement
● Speed
● Velocity
● Time
● Acceleration
Below, let’s also examine a few of these terms:
Displacement and Distance
Displacement is the shortest distance from the initial to the final position of an object. Displacement is a vector quantity as it has both magnitude and direction. This is as opposed to distance, which is a scalar quantity. The other significant difference between distance and displacement is that while distance is the actual length traveled from the initial to the final position, displacement is the shortest distance between the two positions.
Velocity
Velocity can be defined as the displacement of the object in unit time. When the speed of an object is measured in a specific direction, it is termed Velocity. In other words, velocity is speed in each direction. This means that while speed only describes how fast an object moves, velocity offers both the speed and direction of the object. Velocity is measured in meters per second.
Acceleration
Acceleration is the rate of change of velocity with time. When an object speeds up, it is said to have positive acceleration, and when it slows down, it is said to have negative acceleration or retardation. Acceleration is a vector quantity and is measured in meters per second square- m/s2.
Types of Motion in Physics
While studying motion, it is important to recognize that motion can take many forms. Vital among them are:
● Linear
● Translational
● Rotational
● Periodic
● Simple Harmonic
● Projectile
● Oscillatory
Let us look at some of them in some detail:
Linear Motion
As the name suggests, linear motion can be defined as particles moving from one point to another either in a straight line or a curved path. In turn, this motion can take the form of:
- Rectilinear Motion – This is when the path of the motion is a straight line.
- Curvilinear Motion – This is when the path of the motion is curved.
The motion of a car on a road is an example of linear motion.
Rotatory Motion
Once again, as its name suggests, Rotatory Motion refers to a body rotating on its axis. For instance, the motion of the earth or the wheels in an automobile are examples of rotatory motion.
Oscillatory Motion
This kind of motion refers to the motion of a body about its mean position. Examples of oscillatory motion include:
- Movement of a swing
- The pendulum of a clock
- String of a guitar when strummed.
Laws of Motion
Any discussion on motion is incomplete without discussing the 3 seminal laws of motion. Also known as Newton’s laws of motion, based on Sir Issac Newton’s presentation of these laws in the “Principia Mathematica Philosophiae Naturalis.”. The Laws of Motion are:
- Newton’s first law: the law of inertia
Newton’s first law states that if a body is at rest or moving at a constant speed in a straight line, it will remain at rest or keep moving in a straight line at constant speed unless a force acts upon it. In classical Newtonian mechanics, there is no vital distinction between rest and uniform motion in a straight line. This is also known as the law of inertia. Galileo Galilei first formulated the law of Inertia, which René Descartes later generalized.
- Newton’s Second Law
Newton’s second law states that the acceleration of an object depends upon two variables – the net force acting on the object and the object’s mass. While the acceleration of the body is directly proportional to the net force acting on the body, it is inversely proportional to the body’s mass. This means that as the force acting upon an object increases, the acceleration of the object is increased. Similarly, as the mass of an object is increased, the acceleration of the object is decreased.
For a constant mass, force equals mass times acceleration. F = ma.
- Newton’s third law: the law of action and reaction
The law states that for every action, there is an equal and opposite reaction. Essentially, when two bodies interact, they apply forces on one another that are equal in magnitude and opposite in direction.
Influence of Newton’s laws
Newton’s laws are fundamental in layman’s terms since they impact almost everything we notice in everyday life. It is these laws that explain to us, for instance, why you do not float out of your bed or why buildings do not fall. They also explain day-to-day occurrences, such as how cars travel or water flows.
In studying physics, you tend to apply Newton’s 3 Laws to real-life issues.
At Pragyanam, one of the best CBSE schools in Gurgaon, we like to pique the curiosity of our students. It is, in turn, this curiosity that motivates them to learn about several different concepts. Then, with students being taught how to think instead of what to think, we convert them into learners for life.
