Motion and Measurement of Distances
Category : 6th Class
Motion and Measurement of Distances
Synopsis
- Different modes of transport are used to go from one place to another.
- In ancient times, people used the length of a foot, the width of a finger, the distance of a step as units of measurement. This caused variation and inaccuracy and a need to develop a uniform system of measurement arose.
- Now, the International System of Units (S.I. unit) is followed all over the world.
- A unit is a standardized quantity of a physical property, used as a factor to express quantities of that property.
- A standard unit is the measurement value which remains the same even when it is measured by anybody at any place.
- The standard units of length are millimetre (mm), centimetre (cm), metre (m) and kilometer (km).
- The following is the relationship between the units.
\[10\text{ }mm=1\text{ }cm\]
\[100\,\,cm=1\text{ }m\]
\[1000\text{ }m=1\text{ }km\]
- The correct technique of measuring length is the eye being directly in line with the other end of the object as shown in the adjacent figure.
- A thread or string and a ruler are used for measuring the length of a curved line and the circumference of a ball.
Types of motion
- Motion in a straight line is called rectilinear motion.
- A man walking and the motion of a cycle, a bus and that of a car on a straight path are all in translatory motion.
- If the motions of points or parts of an object are along a circular path instead of a straight line path/then the motion of the body is said to be in rotatory motion.
- The to and fro motions of an object about a fixed point is called oscillatory motion.
- Oscillatory motion which is very fast to begin with and soon slows down and comes to rest is called vibratory motion.
