Which record is most informative for a measured length?
- 12.4 cm
- long
- 12.4
Answer and explanation
12.4 cm
It gives both value and unit.
Subjects
Measurement & evidence
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Sample exercises
A length is 0.75 m. Express it in centimetres.
Answer and explanation
75 cm
There are 100 cm in 1 m, so 0.75 × 100 = 75 cm.
Measurements are 18, 20 and 22 seconds. Find their mean.
Answer and explanation
20 s
Their sum is 60 s; divide by 3.
A ruler starts its numbered scale 5 mm from its end. Where should the object start?
- Always at the physical end
- At any number without adjustment
- At the scale's zero mark
Answer and explanation
At the scale's zero mark
The measuring origin is the marked zero, not necessarily the ruler's edge.
Why is writing 12.000000 cm from a coarse ruler misleading?
Answer and explanation
The digits suggest precision the instrument did not establish.
Credit a distinction between displayed digits and measurement resolution.
A balance reads 2 g with nothing on it. Why will averaging many readings not necessarily fix it?
Answer and explanation
The same zero offset can remain in every reading.
A systematic offset is not removed simply by repeating measurements.
Study notes
Measurements, units and sensible precision
Read scales, record units and separate measurements from assumptions.
Grades 5–8Measurements, units and sensible precision · Revision sheet
Read scales, record units and separate measurements from assumptions.
Grades 5–8Physics evidence: uncertainty and proportionality
Interpret patterns without turning a short dataset into proof.
Grades 9–12Physics evidence: uncertainty and proportionality · Revision sheet
Interpret patterns without turning a short dataset into proof.
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