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Know your Physics

by News Echo
3 minutes read

Fundamentals of motion

When a box is on a table, it does not appear to be moving, but it really is. This is so because the table is holding the book and is on the surface of the earth, which is always rotating on its axis and revolving on its part round the sun. As it does so, the book in actual sense is moving. Nobody or object on earth is at absolute rest.

This science of the study of motion done by Galileo Galilee is known as ‘Kinematics’. Some examples of motion are;

i. A car moving from one place to another (point A to point B).

ii. When a ball is thrown up, it moves upwards or downwards.

iii. The simple pendulum of a clock

Types of motion
Motion consists of four basic types viz;

i. Translational or rectilinear motion

ii. Oscillatory motion

iii. Rotational motion

iv. Random motion

Translational or Rectilinear
When a body moves from one point A along the line AB, to another point B, we say that the body is translated from A to B and the motion performed is known as translational motion.

E.g. When a car travels from Lagos to Owerri or an aeroplane flies from Lagos to London, or a student walks from the classroom to the school hall, translational motion is said to be performed.
A<———> B

Oscillatory motion
In this type of motion, a body moves to and fro about a fixed point. If a simple pendulum is displaced slightly from the rest position, A to a new position B and released, it will be noticed that the pendulum swings to and fro i.e. B—»A—»C—»A—»B as shown.

Other examples are vibrations of a plucked guitar string, the children’s swing, the movement of a loaded vertical spring and slightly displaced from its rest position, the cantilever, and the vibrations of the molecules of a solid.

In oscillatory motion, the body does not move entirely away from its original position of rest as it does in translational motion.

Rotational motion
This is the motion of a body which travels in a circle or eclipse and rotates about an axis, e.g. rotation of the earth about its axis, the rotation of the blade of an electric fan about its axis, and the rotation of a top about a central axis.

Random motion
The bodies concerned move in a zig-zag manner. Their movements are not organised. They change continuously so that they do not trace any definite path. This is how the molecules in gases move. An e.g. is the butterfly.
Moving bicycle wheels exhibit both rotational and translational motion.

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