All matter in the universe is constantly in motion, from the
revolution of Earth around the Sun to electrons moving around
the nucleus of an atom. Leaves rustle in the wind. Lava flows
from a volcano. Bees move from flower to flower as they gather
pollen. Blood circulates through your body. These are all examples of matter in motion. How can the motion of these different
objects be described?
To describe an object in motion, you must first recognize
that the object is in motion. Something is in motion if it is
. It could be a fast-moving airplane, a leaf
swirling in the wind, or water trickling from a hose. Even your
school, attached to Earth, is moving through space. When an
object moves from one location to another, it is changing position. The runners shown in Fig. 1
sprint from the start line to
the finish line. Their positions change, so they are in motion.
Fig. 1: When running a race,
you are in motion because your
Determining whether something
changes position requires a point of reference. An object
changes position if it moves relative to a reference point.
To visualize this, picture yourself competing in a 100-m
dash. You begin just behind the start line. When you pass
the finish line, you are 100 m from the start line. If the
start line is your reference point, then your position has
changed by 100 m relative to the start line, and motion
has occurred. Look at Fig. 2
. How can you determine
that the dog has been in motion?
In physics we are concerned with three types of motion: translational, rotational, and vibrational. A car moving down a highway is an example of translational motion
, the Earth spin on its axis is an example of
, and the back-and-forth movement of a pendulum is an example
of vibrational motion
. From everyday experience we recognize that motion represents a continuous change in the position of an object.
The motion in which all the particles of a body move through the same distance in the same time is called translatory motion.
Fig. No.1: Both of the motions are Translatory.
In our study of translational motion, we describe the moving object as a particle regardless of its size.
In general, a particle is a point-like mass having extremely small size
. For example, if we wish to describe the motion of the Earth around the Sun, we can treat the Earth as a particle and obtain reasonably accurate data about its orbit.
As an example on a much smaller scale, it is possible to explain the pressure exerted by a gas on the walls of a container by treating the gas molecules as particles.
There are two types of translatory motions: Rectilinear motion
; Curvilinear motion
. Both of the types are defined and visualized in the Fig. no.1.
are motion of car, Aeroplan, rocket etc.
A rotation is a circular movement of an object around a center (or point) of rotation. Every rigid body has a center of rotation. In the rotation, every point makes a circle around the central point.
Fig. No. 2: Earth rotates around its orbit as it revolves around the sun.
So, there is an equal distance from the center to any point of the shape. if the the body is placed in rotation by applying external force, the center of rotation is always forcing the body to be rotated around itself. It is due to the rotational motion of earth, which continuously alter days and nights by a rotational (circular) motion around its center of mass. But our earth planet also revolves around the sun which continuously alter seasons around the world.
What is Revolutional Motion?
The term revolution is used to describe a motion, wherein an object moves in a circular direction around an object or center, in a fixed path or orbit. It involves travelling around an axis outside the object, i.e. external axis. The distance travelled by an object, in one revolution, around the circle, is nothing but its circumference. The time taken by an object to complete one revolution around the circle is known as the period, represented by T. The revolution of the Earth around the Sun is in the anticlockwise manner, which takes 365 days and 6 hours to complete. It is the only reason for causing seasons to change.
A body moves to and fro about its mean position periodically is called vibratory motion.
Fig. No.3: The Figure shows vibratory motion
Vibratory motion can be described as any object moving/swinging back and forth, moving up and down, pulsating, spinning, or vibrating. swinging
are the example of vibratory motion.