Q1
What is the SI unit of length?
AMetre
BKilogram
CSecond
DLitre
ICSEClass 9 (ICSE)PhysicsCh 1 · Topic 1
Measurements and Experimentation
Accurate measurements using standard units and proper experimental techniques form the foundation of scientific investigation in physics.
Core concept
The SI system uses base units like metre (length), kilogram (mass), and second (time), ensuring consistency in scientific measurement worldwide.
How it works
Precision instruments, like Vernier callipers (accurate to 0.01cm) and screw gauges (accurate to 0.001cm), measure small lengths more precisely than rulers.
Why it matters
Systematic errors (consistent, repeatable errors) and random errors (unpredictable variations) both affect measurement accuracy and must be minimised.
Key detail
Proper experimental technique, including repeated measurements and careful observation, ensures reliable, accurate scientific results.
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• SI units: metre, kilogram, second.
• Vernier callipers measure to 0.01cm accuracy.
• Screw gauges measure to 0.001cm accuracy.
• These are more precise than standard rulers.
• Systematic errors are consistent, repeatable.
• Random errors are unpredictable variations.
• Both affect measurement accuracy.
• Proper technique ensures reliable results.