Table of Contents

## Definition of Mechanics Physics:

Mechanics Physics is the branch of physics that is concerned with the motion of objects under the action of forces and also when the bodies are at rest.

When force is applied to a body it brings some change in distance, displacement, or position of a body.

Mechanics are considered to b first of the exact sciences to b developed. It is based on mathematical discipline and gives the beautiful quantitative detail of the motion of the moon, stars, planets, and satellites, etc.

While studying mechanics we must have to familiar with some terms. These are:

**Force:**

Force is the interaction among bodies that can change the motion and position of a body. **The SI unit of force is newton denoted as ‘N’. **There are different formulas to find force according to the given conditions.

**Distance and displacement:**

Distance is a scalar quantity that describes the whole path when the body moves while displacement is a vector quantity that describes the shortest distance between two points.

**Velocity:**

The velocity of a body is the rate at which a body changes its position. **SI unit of velocity is m/s.**

We can find the velocity of a body by using formula:

**V=d/t**

**Acceleration:**

Acceleration of a body is the rate at which the body changes its velocity. **SI unit of acceleration is m/s².**

The formula to find acceleration is:

**a=v/t**

## Newton’s laws of motion:

### Newton’s First Law of Motion:

Newton’s first law of motion states that if a body is at rest/ in uniform motion remains at rest/in uniform motion unless some external force acting upon it.

### Newton’s Second Law of Motion:

Newton 2nd law of motion states that when a force acting on a body, the force is directly proportional to the acceleration and mass of a body. The velocity of a body remains constant.

The formula of second law of motion is given below:

**f=ma**

### Newton’s Third Law of Motion:

Newton’s 3rd law of motion states that for every action there is always an equal reaction but on the opposite side.

**In 1020 a Muslim scientist Ibn e Sina published his book on the theory of motion named “The book of healing” in which he describes projectile motion in detail.** He distinguished between force and inclination. He argued that when the object is on the opposite side of its natural motion it gains inclination.

In the beginning, many theories are proposed and rejected many times. At that time the main problem was the projectile motion that no one can be solved due to lack of accurate information about the projectile motion.

**What are force and inclination?**

Force means the interaction that will change the position or motion of a body. A force has both the velocity and acceleration that is the cause force is a vector.

Inclination means a tendency to a particular aspect, state, character, or action.

## Types of Mechanics Physics:

Historically mechanics is divided into two types.

1. Classical mechanics

2. Quantum mechanics

### Classical Mechanics:

Classical mechanics came first as compared to Quantum mechanics. The concept of classical mechanics originated when Issac Newton proposed the laws of motion.

Classical mechanics deals with the objects that are in rest or moving with some velocities. It also describes the equilibrium of bodies when equal forces acting on a body. It is applicable to solve problems that are concerned with the macroscopic processes. These macroscopic processes are used to find distance, displacement, acceleration, velocity, mass, force, or time.

If we have given the state of an object it is quite easy to predict how was the movement of an object in past also how it will move in the future, this is possible with the help of classical mechanics. We study the objects that are not highly massive and their speed can’t approach the speed of light, in such type of cases classical mechanics gives us an accurate result.

Classical mechanics always describes the objects of non zero size. For example, the center of mass and the degrees of freedom.

### Quantum Mechanics:

Quantum mechanics deals with the motion of a body and forces applied to a body. In such types of mechanics, we usually examine objects at the atomic and subatomic levels. For example, the diameter of the atom could be examined by following the laws of quantum mechanics.

Quantum mechanics provide a description of the probability of obtaining possible outcomes rather than assigning a definite value.

The study of Quantum mechanics cleared the essential methodology of physics. It gives accurate result in every situation in which it has been applied.

Quantum mechanics describes the objects that have both the properties of the wave as well as properties of particles. Properties of waves are frequency, wavelength, and spread over space. While the properties of a particle include countability and also the degree of location.

These two types were the earlier types of mechanics that are also familiar and have an important role in physics.

But the modern type of mechanics includes dynamics and kinematics.

### Dynamics:

Dynamics is the sub-branch of mechanics, not only mechanics, this branch is developed in classical mechanics and also deals with the motion of a body in the term of force, mass and momentum. The base of dynamics is the newton 2nd law of motion.

Second law of motion states that when one body exerts a force on another body, as a result the other body also exerts equal but opposite force.Simply means there is always a reaction to every action.The whole dynamics is related to this law and describes not only action of forces but also the reactions that occurs as a result of every action.

The motion of objects is not the same. Some objects/bodies move linearly, while some move in a circular path.

**Also Read:**

Guide about Biophysics:

Complete Guide about Optics Physics:

At the base of different paths of motion, dynamics is further categories into linear dynamics and rotational dynamics. Linear dynamics concern with the motion of objects in a line. The line may be straight or curved, it doesn’t matter the shape of the line while Rotational dynamics concern the motion in a circular or round path. The quantities that we can describe/find in linear dynamics are force, velocity, acceleration, mass, and inertia, etc.

Whereas the quantities of rotational dynamics include torque, inertia, circular momentum, angular moment and angular velocity, etc.

### Kinematics:

Kinematics is a subdivision of mechanics and also developed in classical mechanics as dynamics. In kinematics, we concern only with the effect of force and motion of a body without knowing the reason that is the cause of the motion of a body.

Kinematics mostly concerned with the geometry of motion. All of the kinematics problems started with given the geometry of a system, and with the help of given information we can find out the initial conditions. Kinematics is usually used in astrophysics that describes the motion, speed, direction, and location of asteroids in space.

The description of kinematics mostly includes that rate at which the body moves and also the rate at which speed of the object changes. The rate of change of position of a body is known as the velocity of the body. And the rate at which velocity of a body changes, known as the acceleration of a body.

**Conclusion:**

Mechanics is the branch of physics that concern with motions of bodies and also about the cause of motion. Subdivisions of mechanics are classical mechanics and quantum mechanics depending on the difference of motion of bodies. Advanced Classical mechanics is now further divided into dynamics and kinematics.