Measurement of Length and Motion

Class 06 Science

Hand spans and other similar units, such as length of hand, foot, fist or fingers, differ from person to person. Thus, there is a need for such a unit for which measurements of the same length made by different people do not differ.

Standard Units

Several systems of units evolved with time in different parts of the world. However, when people started travelling from one place to another, it created a lot of confusion. This led to the different countries coming together and adopting a set of standard units of measurement. The system of units now used is known as the ‘International System of Units’ or SI units.

The SI unit of length is metre. Its symbol is m. One metre (m) is divided into 100 equal divisions. Each division is called a centimetre (cm). 1 cm length can be further divided into 10 equal parts. The length of one of these smaller parts is called a millimetre (mm). 1 mm is equal to one-tenth of a centimeter (1 mm = 0.1 cm).

For measuring larger lengths, we use a larger unit called a kilometre (km) which is equal to 1000 metres. For measuring smaller lengths, we use units such as centimetre or millimetre.

1 km = 1000 m

1 m = 100 cm

1 cm = 10 mm

Measuring the Length of Curved Line

In the case of a curved line, measurements can be made with the help of a flexible measuring tape or by using a thread.

The thread can then be straightened and its length can be measured using a metre scale.

Motion

When distance is stated with respect to a fixed object or point, then this point is called a reference point.

An object is said to be in motion if its position changes with respect to the reference point with time. If an object is not changing its position with respect to the reference point with time, it is said to be at rest.

Types of Motion

When an object moves along a straight line, its motion is called linear motion.

When an object moves along a circular path, its motion is called circular motion.

When an object moves to and fro about some fixed position, its motion is called oscillatory motion.