# 6th Class Science Motion Motion and Measurement of Distances

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.

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