Measurement of Length and Motion Class 6 Notes

Measurement of Length and Motion: Measurement is the process of finding out how big, long, or far an object is. It is used for comparing the size of different objects. The length of an object tells us how long or short it is. Measurement of length is known as the measurement of linear dimensions. Motion is a change in the position of an object with respect to time. It is a fundamental concept in physics. Measurement and motion are both important in science as well as in our day-to-day lives.

What is Length?

Length is the distance between two points. Length may be short as well as long. For example, the length of a pencil is short, but the distance between two cities is long. We use different measuring instruments to measure the length of different objects on the basis of their size.

Units of Length

The standard unit of length is the metre (m). The other units related to the metre are:

• 1 kilometre (km) = 1000 metres

• 1 metre (m) = 100 centimetres (cm)

• 1 centimetre (cm) = 10 millimetres (mm)

Instruments Used to Measure Length

Different instruments are used for measuring length depending on the situation:

• Ruler or Scale: Used for measuring small objects such as a pencil, a notebook, etc.

• Measuring Tape: Used by a tailor, engineer or builder for measuring larger or curved surfaces.

• Metre Rod: Used in laboratories or shops for accurate measurement of objects.

• Odometer: It is used in vehicles for measuring the distance travelled by the vehicle in kilometres.

What is Motion?

Motion means a change in the position of an object with respect to time. If the position of an object changes with respect to time, it is said to be in motion. For example, when a bus is moving, a bird is flying, or a fan is rotating, all these are examples of motion.

Types of Motion

• Rectilinear Motion: When an object moves along a straight line.

• Example: A car moving on a straight road or a train running on straight railway tracks.

• Circular Motion: When an object moves around a fixed point in a circular path.

• Example: The blades of a fan or the Earth revolving around the Sun.

• Periodic Motion: When an object repeats its motion after a fixed interval of time.

• Example: The pendulum of a clock or the movement of a swing.

An object can have more than one type of motion. For example, a rolling wheel moves in a straight line as well as rotates about its own axis.

Rest and Motion

If the position of an object changes with respect to time, then it is said to be in motion. If the position of an object does not change with time, then it is said to be at rest. For example, if a car is parked, it is at rest. When it starts moving, it comes into motion. Motion and rest are relative; that is, an object can be in motion with respect to one object and at rest with respect to another object.