The Right Tool for the Job
Rulers, tapes, balances, clocks — measuring like a scientist
What this lesson covers
Why it matters
Would you measure the road to Pune with your 15-cm ruler? You could — it would take a week. Every job has its right tool and its right unit.
Predict first
Which is the best unit for the distance between two cities?
Units come in sizes: mm for ants, cm for pencils, m for rooms, km for journeys — and each quantity has its own device. (Mass, by the way, simply means how much MATTER a thing contains.)
- kilometres — correct
- centimetres
- hand-spans
What you do
Match every measuring job to its proper device and unit — a scientist never brings a ruler to weigh a bag.
Check yourself
1 metre = …
And 1 km = 1000 m — the ladder climbs in easy steps of 10, 100, 1000.
The thickness of your fingernail is closest to…
Small things, small units — the mm is the fingernail's rung.
Your school bag's mass is about…
A sense of scale is a superpower: grams for erasers, kilograms for bags.
- 100 centimetres — correct
- 10 centimetres
- 1000 centimetres
- 1 millimetre — correct
- 1 centimetre
- 1 metre
- 4 kilograms — correct
- 4 grams
- 400 kilograms