Units, measuring length correctly, and kinds of motion. Read, watch it move, sort, then play.
What it is
Long ago people measured with hand spans and foot lengths, but these differ from person to person. So we use standard units: millimetre, centimetre, metre and kilometre.
Why it works
Standard units mean a measurement is the same for everyone, everywhere, so results can be shared and trusted. The metre is the basic SI unit of length.
Why it matters
This lets a tailor, a builder and a shopkeeper all agree on a length.
A few examples
A pencil is measured in centimetres. A road in kilometres. A coin's thickness in millimetres.
What it is
The units link together neatly: 1 cm = 10 mm, 1 m = 100 cm, and 1 km = 1000 m.
Why it works
Because they go in tens, hundreds and thousands, we can change one unit into another by simple multiplying or dividing.
Why it matters
This helps us compare lengths given in different units.
A few examples
1 metre is 100 centimetres. 1 kilometre is 1000 metres.
What it is
For each thing we measure, one unit fits best: tiny things in millimetres, everyday things in centimetres or metres, and long distances in kilometres.
Why it works
Using a fitting unit keeps the number sensible, not a huge or tiny figure, so it is easy to read and understand.
Why it matters
Picking the right unit is a real skill we use whenever we measure.
A few examples
A seed in mm. A book in cm. A room in m. A journey in km.
What it is
Motion comes in types. Straight-line (rectilinear) motion goes along a line, circular motion goes round and round, and to and fro (periodic) motion repeats back and forth.
Why it works
We name motion by the path it follows. A car goes straight, a wheel turns in a circle, a pendulum swings back and forth, each a different pattern.
Why it matters
Describing motion helps us understand how things move all around us.
A few examples
A car shows straight motion. A fan shows circular motion. A swing shows to and fro motion.
What it is
To measure well, place the object's start at the zero mark, keep the scale straight along it, and put your eye directly above the mark you read.
Why it works
These steps stop mistakes. Looking from an angle, or starting off the zero, gives a wrong reading, so careful placing matters.
Why it matters
Careful measuring gives numbers we can rely on.
A few examples
Line up the zero, keep the ruler straight, and look straight down to read.
What it is
Before measuring, it helps to estimate, that is, make a sensible guess of the length using units you know.
Why it works
Estimating builds a feel for size, so you notice if a measurement looks wrong, like a door being 2 metres and not 2 centimetres.
Why it matters
A good sense of size is useful every day, in shopping, building and travel.
A few examples
A door is about 2 m. A pencil about 15 cm. A grain of rice about 5 mm.
A car moves in a straight line, a wheel turns round, a pendulum swings to and fro. All moving on their own.
Drag each into the kind of motion it shows. sorted 0/6
Have a go first, then tap to see the clear steps.
Q1. Which unit is best for measuring the length of your classroom?
Q2. How many centimetres are there in 1 metre?
Q3. A spinning ceiling fan shows which kind of motion?
Q4. When reading a ruler, where should your eye be?
Q5. How many metres are there in 1 kilometre?
Q6. Is a door about 2 metres or 2 centimetres tall?