Definition on motion and rest-
An object is said to be in motion if it changes its position with respect to its surroundings in a given time.
Motion is always observed and measured with a point of reference.
All living things show motion..Whereas the non living things show motion only when some force is acting on it.
The motion in which all points of a moving body move uniformly in the same line or direction is called translatory motion.
If a body moves in a straight line it is said to have rectilinear motion.
If a body moves along a curved path, it is said to have curvilinear motion.
An object is said to be in circular motion when it moves around a fixed point called AXIS.
When a body as a whole moves in a circular path its motion is called revolution…and the body is said to revolve .
E.g: the earth revolves around the sun.
When a body undergoes translatory motion in such a way that its parts cover different distances in a given time, it is said to have rotatory motion.
Irregular motion of a body in which the direction of motion is not fixed is called random motion.
When a body moves to and fro about a fixed point, it is said to be in oscillatory motion.
Sometimes the whole object does not show to and fro motion, but a part of it shows this motion, such a motion is termed as vibratory motion. This motion is actually a very fast to and fro motion.
All musical instruments show vibratory motion. During this motion a change in shape and size takes place.
When the same motion repeats itself after equal intervals of time, we call it periodic motion.
MANY TYPES OF MOTION
DRAWING WATER FROM WELL:
The pulley on which the rope runs has a circular motion and the bucket has a linear motion.
MOTION OF A SEWING MACHINE:
The needle of a sewing machine oscillates and its wheel rotates in a circular motion.
MOTION OF EARTH:
The earth revolves round the sun, thus showing circular motion. It rotates around its axis showing rotatory motion. Both the above motions are repeated after a fixed interval of time…so it shows periodic motion too.
When a person rides a bicycle, the cycle and the cyclist show translatory motion but the wheels show rotatory motion.
When a screw is screwed into a box then it shows both rectilinear and rotatory motion.