Errors, precision and combining uncertainties
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The teaching part (1 min) is free to watch. A free account opens the whole lecture: 1 worked example, 4 practice questions, 3 real past-paper questions with the answers explained, the mistakes that lose marks, the full-marks tip, a one-card summary and a quick quiz.
What this lecture covers
- Every measurement is a range
- Two kinds of error
Read the transcript of the teaching part
Last time
Before we start: last time, in Scalars, vectors, adding and resolving, you learned these points. Here they are again on one card. Keep them in mind, because today builds on them.
Every measurement is a range
Measure a table with a metre rule and you might say one point two zero metres. But is it exactly that? A better statement is one point two zero, plus or minus zero point zero one. Physics reports a range, not a perfect number.
Two kinds of error
A random error makes repeated readings scatter about the true value, some above and some below. Averaging many readings reduces the effect of random errors. A systematic error shifts every reading the same way, so they are all too high or all too low. Averaging does not remove it. A zero error on a micrometer is a systematic error. We remove it by calibrating or correcting the zero.
How often it comes up
How often Cambridge has asked each part, counted by ExamYard from every past paper in its question bank: Combining uncertainties · Precision and accuracy · Systematic and random errors · Combining uncertainties.
The whole chapter: Physical Quantities and Units, Physical Quantities and Units.
Chapter 1.1: Errors and uncertainties
- Errors, precision and combining uncertainties 5 min
Also for A Level Physics 9702
Which topics come up most in A Level Physics 9702 past papers, counted from every paper since 2004: Paper 1 topic frequency, Paper 2 topic frequency.