# Ch – 10 Motion And Measurement Of Distances

• Long ago people did not have any means of transport.
• They used to move only on foot and carry goods on their back.
• Later on they began to use animals for transportation.
• Invention of the wheel made a great change in modes of transport.
• The invention of steam engine led to the development of new means of transport.
• The early years of 1900 saw the development of aeroplanes.
• Measurement means the comparison of an unknown quantity with some known quantity.
• The fixed quantity is known as unit.
• Hand span, foot span, cubit are some of the ancient methods of measurement and are unreliable.
• A cubit as the length from the elbow to the finger tips was used in ancient Egypt.
• People also used the “foot” as a unit of length in different parts of the world.
• People measured a “yard” of cloth by the distance between the end of the outstretched arm and their chin.
• The Romans measured with their pace or steps.
• In ancient India, small length measurements used were an angul (finger) or a mutthi (fist).
• In 1790, the French created a standard unit of measurement called the metric system.
• The system of units now used is known as the International System of Units (SI units).
• The motion in which objects move in straight line are called rectilinear motion. Eg: Soldiers in march past.
• In circular motion, the object moves such that the distance from a fixed point remains same. Eg: The blades of an electric fan.
• The motion in which objects keep on repeating its motion after some time is known as periodic motion. Eg: Movement of pendulum.