Units, Measurement & Significant Figures
Key SI units, prefixes, conversions, and sig fig rules for exam success.
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Questions Covered in This Set
10 cards to master
What are the SI base units for length, mass, and time?
Metre (m), kilogram (kg), and second (s).
What is a joule expressed in base units?
J = N·m = kg·m²/s² (so work = force × distance).
How many cm³ are in 1 m³?
1 000 000 cm³ (since 1 m = 100 cm, cubed = 10⁶).
Convert 72 km/h into m/s.
72 × 1000 ÷ 3600 = 20 m/s.
How many sig figs in 0.0042?
2 — leading zeros never count.
How many sig figs in 1.200?
4 — trailing zeros after a decimal point count.
Sig fig rule for multiplication and division
The answer takes the fewest sig figs of any input (4.56 ÷ 1.2 = 3.8).
Sig fig rule for addition and subtraction
Match the fewest decimal places (12.11 + 0.3 = 12.4).
Write 0.00046 m in scientific notation.
4.6 × 10⁻⁴ m (form a × 10ⁿ with 1 ≤ a < 10).
A density of 1 g/cm³ equals how many kg/m³?
1000 kg/m³.
