Mechanics is the branch of Physics that concerns with the study of the motion of macroscopic objects. Here are some of the most common terms associated with Mechanics:

- Kinematics – deals with describing the motion
- Dynamics – deals with the causes of the motion
- Statics- deals with the study of objects at rest
- Kinetics- deals with the relationship between the motion of the objects and forces acting on those objects

## Kinematics

As described above, Kinematics is that division of Mechanics that is concerned with the study of the motion of objects without taking into consideration the forces that are responsible for that motion. Now, we will be looking at the various definitions related to the Kinematics. We will study what is a particle, what are the states of **rest and motion** and what are one-dimensional, two-dimensional and three-dimensional motion. So, let’s begin!

A *particle* is basically a piece of matter that has just a position without any linear dimension linked to it. Particles can be categorized as- macroscopic particles, microscopic particles and subatomic particles.

The state of *rest* is when a body/object does not make any change in its position with respect to its surroundings with time.

In contradiction, the state of *motion* is when a body/object changes its position with respect to its surroundings with time.

As motion is linked with the change in position of the object, in order to study and understand motion, we need to study about the “change in position” i.e. the x,y,z coordinates of the object in relation to its environment. It is considered to be a change in motion if the position of the object changes in one, two or all three coordinates with time.

### a. One-Dimensional Motion

In this type of motion, just one of the three coordinates tracing the position of the object changes with time in relation to its surroundings.

Examples: a runner running in a straight line, an ant moving in a straight line

### b. Two-Dimensional Motion

In this type of motion, two of the three coordinates describing the position of the object change with time in relation to its surroundings.

Examples: motion in a plane, circular motion, motion of an ant moving on the top surface of table

### c. Three-Dimensional Motion

In this type of motion, all of the three coordinates describing the position of the object change with time in relation to its surroundings.

Examples: the motion of an aero-plane in the sky, the motion of a flying kite

## Dynamics

Dynamics is that branch of Mechanics that deals with the study of motion and the causes of that motion. It takes into consideration the physical factors that affect the motion- **momentum**, force, mass and energy.

Mass is the resistance of the body to change of motion.

Energy is the capability to do work.

Momentum is defined as the mass in motion. Every object has mass. So, if an object is moving, then it has momentum. Momentum is the product of mass of the particle/object and velocity.

Force is the push or pull on an object, which when unopposed, changes the motion of an object.

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