Measurement of Length and Motion
Class 6 · Science
5 ideas in Class 6 Science, explained in plain words, with games and quizzes to practise.
Why We Need Standard Units
Part of: Units of length
Long ago people measured with hands, feet and fingers. A length is told in two parts: a number and a unit, such as 12 handspans. But a big hand and a small hand give different counts for the same table, so the result depends on who measures.
Why it matters. Children see why a shared unit is needed. Without it, a shopkeeper and a customer, or a builder and a carpenter, could never agree on a length.
Try it in two minutes
- Ask your child and a grown-up to measure the same sofa in handspans. Write both numbers.
- Ask: why are the numbers different even though the sofa is the same?
- Now measure it with one ruler or tape. Ask: do you both get nearly the same answer now?
Try at home. Ask your child to measure the length of a bed in footlengths and then ask a sibling or parent to do the same, and discuss the difference.
SI Units and Conversions
Part of: Units of length
The metre is the standard unit of length. A metre is cut into 100 centimetres, and a centimetre into 10 millimetres. For long distances we use the kilometre, which is 1000 metres. Pick a unit that fits the size: millimetres for a coin's thickness, kilometres for a journey between towns.
Why it matters. Everyday life uses these units for cloth, heights, distances and recipes for crafts. Children who can switch between them avoid big mistakes, such as thinking 1 km is 100 m.
Try it in two minutes
- Show a 15 cm ruler. Ask your child to find the smallest part on it and say what it is called.
- Ask: how many of these small parts make one centimetre?
- Ask your child to say whether a pencil, a room and a road are measured best in mm, m or km.
Try at home. Ask your child to measure three things at home, one in millimetres, one in centimetres and one in metres, and to write each with its unit.
Using a Scale the Right Way
Part of: Measuring length correctly
A good measurement needs the right tool and the right method. Keep the scale touching the object along its length, and look straight down at the mark you are reading. If the end of the scale is worn, start from a clear mark such as 2.0 cm and subtract. A curved line can be measured by laying a thread along it and then straightening the thread.
Why it matters. Many small mistakes in length come from slanted eyes, a gap between scale and object or a missed zero. Careful habits give results that others can trust.
Try it in two minutes
- Ask your child to measure a pencil with a ruler, first looking from the side and then from straight above. Ask: did the reading change?
- Place the ruler so that its zero end is not used. Start at 2 cm and ask your child how to find the length.
- Lay a thread along a curved line in a drawing, straighten it and measure it.
Try at home. Ask your child to find the length of the curved edge of a plate or glass base using a thread and a ruler.
Reference Point and Motion
Part of: Position and motion
To say where something is, we need a starting point to compare with, called a reference point. If a bus stop is 5 km from your house, your house is the reference point. An object is moving if its distance from the reference point keeps changing, and at rest if it does not.
Why it matters. Without a reference point, descriptions such as near or far give different answers for different people. This idea explains why a passenger can be still and moving at the same time.
Try it in two minutes
- Ask your child how far the kitchen is from the front door, then from the bedroom. Note that the answers differ.
- Say: now let us pick the front door for both. Do we agree?
- On a walk or in a car, ask: is the person next to you moving compared with you? Compared with a tree?
Try at home. Ask your child to describe the position of a toy in the room using two different reference points.
Kinds of Motion
Part of: Position and motion
Things move in different ways. A ball dropped straight down moves along a straight line, which is linear motion. A merry-go-round moves along a circle, which is circular motion. A swing goes to and fro about a fixed position, which is oscillatory motion. Circular and oscillatory motion repeat again and again, so they are called periodic.
Why it matters. Sorting motion into kinds trains children to observe carefully and give reasons. It also prepares them to understand machines, clocks and playground equipment.
Try it in two minutes
- Tie a small toy to a thread. Let it hang, push it gently and watch it swing to and fro. Ask: which kind of motion is this?
- Whirl it slowly in a circle (with enough space). Ask: how is this different?
- Roll a ball along the floor in a straight line. Ask your child to name the kind of motion.
Try at home. Ask your child to list two things in a park that move in each of the three ways and to give a reason for each choice.
What your child will practise
- Kinds of Motion: Jungle Quest (Collect the Answer)
- Reference Point and Motion: Space Quick Fire (Quick Fire)
- SI Units and Conversions: Space Quest (Flip and Match)
- Using a Scale the Right Way: Desert Puzzle (Clue Puzzle)
- Why We Need Standard Units: Jungle Quick Fire (Quick Fire)
- Quiz: Kinds of Motion (8 questions)
- Quiz: Reference Point and Motion (8 questions)
- Quiz: SI Units and Conversions (8 questions)
- Quiz: Using a Scale the Right Way (8 questions)