KINEMATICS- DISTANCE AND DISPLACEMENT
Introduction:
Kinematics is the science of describing the motion of objects using objects, diagrams, numbers, graphs, and equations. Kinematics is a branch of mechanics. The goal of the study of kinematics is that to develop the basic idea about the motion of real-objects.
In this lesson, we will investigate the words used to describe the motion of objects. That is, we will focus on the language of kinematics. The hope is to gain a comfortable foundation with the language that is used throughout the study of mechanics. We will study such terms as scalars, vectors, distance, displacement, speed, velocity and acceleration. These words are used frequently to describe the motion of objects.
Basically, Kinematics is the study of the relationship between displacement, velocity, acceleration and time of a given motion, without considering the forces that cause the motion.
REST AND MOTION
Rest:
An object is said to be at rest if it does not change its position with respect to its surroundings with time.
Examples for the State of Rest:
1. A book lying on table will not change its position if it is not disturbed. So, it is in state ofrest.
2. A bench in a park fixed under a tree is at rest as there is no change in its position.
Therefore, when the position of a body with respect to its surroundings does not change with time, the body is said to be at rest.
Ex: sleeping, standing, staring, sitting, stopped vehicle, stopped clock, book on table, statue
Motion:
An object is said to be in motion if position changes with respect to its surrounding & time.
Ex: Walking, jumping, dancing, driving, cycling, drinking, playing, Swimming, , writing & throwing ball
Examples for the state of Motion:
1. When a moving car changes its position with respect to a tree or a lamp post by the side ofthe road, the car is said to be in motion.
2. A flying bird is also said to be in motion as it changes its position with respect to stationary objects such as trees.
Hence, when the position of a body with respect to its surrounding changes with time, the body is said to be in motion.
Frame of Reference:
Suppose an object is placed on the table, it can be said that the object is at rest. If a person is standing on the moon, he will find that earth is changing its position continuously and so are the table and the object. Thus, to locate the position of anything one needs to define a frame of reference. For instance, if we take the earth as a reference, then the object is at rest but if the moon is taken as reference, the object is in motion.