0.6 · Preface · Tools: unit conversion
Converting units
Worked examples, then practise with fresh numbers.
SL+HLMedium15 minFree
Hook
A speedometer says 36 km/h. A physics problem needs m s⁻¹. Same speed, different unit. How do you switch without slipping?
The method
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72 km/h in m s⁻¹ is…
Check 2 of 3
250 cm² in m² is…
Check 3 of 3
2 h in seconds is…
Apply
Convert 500 cm³ to m³, and explain why the factor is 10⁻⁶ and not 10⁻².
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Remember earlier lessons
From lesson 0.5
Pressure is measured in…
From lesson 0.4
micro means…
Summary card
Key points
- • Write what each unit is worth in SI first.
- • Convert lengths before squaring or cubing.
- • cm² → m²: × 10⁻⁴. cm³ → m³: × 10⁻⁶. km/h → m s⁻¹: ÷ 3.6.
Formulas
- 1 cm² = 10⁻⁴ m²
- 1 cm³ = 10⁻⁶ m³
- v(m s⁻¹) = v(km/h) ÷ 3.6
Key terms
- Conversion factor :
- what one unit is worth in another
Common errors
- • Using 10⁻² for an area or a volume.
- • Multiplying instead of dividing when going from km/h to m s⁻¹.
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