Chapter 5: Measurement of Length and MotionClass 6 Science — summary, notes, extra questions & NCERT solutions

Summary

This chapter explains how we measure length and how we describe motion. It begins with the everyday problem that measuring with body parts such as a handspan (balisht), foot, or angula gives different results for different people, so we need standard units that do not vary. The world solved this by adopting the International System of Units (SI), in which the SI unit of length is the metre (m); one metre is divided into 100 centimetres, each centimetre into 10 millimetres, and a kilometre equals 1000 metres (1 km = 1000 m, 1 m = 100 cm, 1 cm = 10 mm). The chapter teaches the correct way to measure: placing the scale in contact with the object along its length, keeping the eye directly above the point being read to avoid error, and, if the zero end is broken, measuring from a full mark and subtracting. Flexible measuring tapes and threads are used for curved lines and round objects. The chapter then turns to position and motion. A position is always stated with respect to a fixed point called a reference point, illustrated by kilometre stones that show distance from a city. An object is in motion if its position changes with respect to a reference point with time, and at rest if it does not; whether something is moving can depend on the chosen reference point, as a bus passenger is at rest relative to the bus but in motion relative to a building outside. Finally, the chapter classifies types of motion: linear motion (along a straight line), circular motion (along a circular path), and oscillatory motion (to and fro about a fixed position). Both circular and oscillatory motion are periodic because they repeat after a fixed interval of time.

Key terms

Extra questions & answers

Activity 5.1: Let us measure

Activity 5.2: Let us explore

Activity 5.3: Let us explore

Activity 5.4: Let us investigate

Activity 5.5: Let us investigate

Activity 5.6: Let us investigate

Activity 5.7: Let us identify

Let us enhance our learning

Learning further

Explore interactively