# Introduction

## Introduction

Motion draws our attention. Motion itself can be beautiful, causing us to marvel at the forces needed to achieve spectacular motion, such as that of a dolphin jumping out of the water, or a pole vaulter, or the flight of a bird, or the orbit of a satellite. The study of motion is kinematics, but kinematics only describes the way objects move—their velocity and their acceleration.
Dynamics considers the forces that affect the motion of moving objects and systems. Newton’s laws of motion are the foundation of dynamics. These laws provide an example of the breadth and simplicity of principles under which nature functions. They are also universal laws in that they apply to similar situations on Earth as well as in space.

## Introduction

Motion is one of the significant topics in physics. Everything in the universe moves. It might only be a small amount of moment and very-very slow, but movement does happen. Even if you appear to be standing still, the earth is moving around the sun, and the sun is moving around our galaxy.
An object is said to be in motion if its position changes with time.”
The concept of motion is a relive one and a body that may be at in motion relative to one reference system, may be at rest relative to another.

There are two branches in physics that examine the motion of the object.
1. Kinematics: It describes the motion of objects, without looking at the cause of the motion.
2. Dynamics: It relates the motion of objects to the forces which cause them.

Point object
If the length covered by the objects are very large in comparison to the size of the objects, the objects are considered point objects.

Reference Systems
The motion of a particle is always described with respect to a reference system. A reference system is made by taking an arbitrary point as origin and imaging a co-ordinate system to be attached to it. This co-ordinate system chosen for a given problem constitutes the reference system for it. We generally choose a co-ordinate system attached to the earth as the reference system for most of the problems.

Types of Motion
1. One Dimensional Motion
If only one out of three coordinates specifying the position of the object changes with respect to time, then the motion is called one dimensional motion.
For instance, motion of a block in a straight line motion of a train along a straight track a man walking on a level and narrow road and object falling under gravity etc.

2. Two Dimensional Motion
If only two out of three coordinates specifying the position of the object changes with respect to time, then the motion is called two dimensional motion.
A circular motion is an instance of two dimensional motion.

3. Three Dimensional Motion
If all the three coordinates specifying the position of the object changes with respect to time, then the motion is called three dimensional motion.
A few instances of three dimension are flying bird, a flying kite, a flying aeroplane, the random motion of gas molecule etc.

## Introduction

The physical quantities like work, temperature and distance can be represented in day to day life wholly by their magnitude alone. However, the relation of these physical quantities can be explained by the laws of arithmetic. In order to represent physical quantities like acceleration, displacement, and force, the direction is equally essential along with the magnitude.

Motion in a plane includes linear motion, rotational motion, and projectile motion. This lesson will focus on two-dimensional, linear motion of a single object, and linear motion of two objects moving relative to each other. In both scenarios unit-vectors will be utilized to organize the displacements, velocities, and accelerations of the object(s); and techniques will be taught that help to solve these types of kinematics problems.

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