Unit 1
Measurement.
SI units and prefixes, reading a scale, significant figures, directed quantities, and errors in repeated readings.
Before this unit
- Ratio and scale Mathematics
The unit, lesson by lesson
Lessons
6 lessons · 35 practice questions · about 3 hours
SI units
Every measurement is a number and a unit: seven base units, prefixes from nano to giga, units built from the base units, and checking a formula by its units.
Reading a scale
Every measuring instrument reads to its smallest division: reading to the nearest mark, the uncertainty of a reading, measuring from a mark other than zero, and how to write the result down.
Significant figures
The digits a measurement really tells: how to count them, zeros that count and zeros that don't, scientific notation that shows how many digits were measured, and how many digits to keep after multiplying and adding.
Scalars and vectors
Some quantities need only a number and a unit, and some need a direction too: a vector as an arrow, speed and velocity, distance and displacement, and adding moves.
The scientific method
A good hypothesis predicts something that could turn out wrong: a prediction before the test, one clear miss that refutes, an agreement that does not prove, and a sharper test that catches a small effect.
Random and systematic error
Every repeated measurement gives a slightly different reading: the spread of one reading, the standard error of the mean and its √n, and a systematic error that no number of measurements fixes.