PhysicsClass 111 markeasy
Units and Measurements
How many significant figures are there in the measurement 0.00420 m?
Reveal model answer + marking pointsHide answer▾
Three significant figures (4, 2 and the trailing 0). Leading zeros are not significant; a trailing zero after the decimal point is significant.
Marking-scheme points
- ✓Leading zeros: not significant
- ✓Trailing zero after decimal: significant
- ✓Answer = 3
The concept
Significant figures show how precisely a quantity was actually measured.
Why it matters
They stop you reporting false precision - vital in labs, medicine and engineering.
💡 Memory trick
Leading zeros DON'T count; trailing zeros after a decimal DO. So 0.00420 has 3.