Show model answer and explanation
0.01
The uncertainty is one hundredth of the reading.
Class 9 · English Medium · Cambridge · Physics
Practical investigation and numerical reasoning
Combine uncertainty, graphs and dimensional checks in a numerical investigation.
Shared cross-level core and stretch unit. Start with the core questions, then use the stretch example for deeper work. The same unit is available in related class and board pathways; it is not a full grade-specific or examination-specification course. A teacher should select the appropriate depth and further topics.
Learn the idea
A measurement result needs its unit and a reasonable statement of uncertainty. A graph should label both axes and display the relationship being tested. A best-fit gradient is not necessarily the slope between the first and last raw readings. Dimensional consistency can detect some mistakes but cannot prove a model correct.
Worked example
For length 20.0 ± 0.2 cm, the stated absolute uncertainty is 0.2 cm and its fraction of the reading is 0.2/20 = 0.01, or 1%. This expresses precision under the stated method, not every possible source of error.
- Define the measured quantity and instrument.
- Calculate with units and justified precision.
- Explain uncertainty and alternative causes.
Stretch example
If y = kx², a plot of y against x² should be linear under that model. Residuals are the observed values minus fitted values; a curved residual pattern suggests that the proposed relationship may be incomplete.
Your written practice
Show your working on paper and enter your answer here. If it does not match, compare the model and try again.
Show model answer and explanation
3
(12−3)/(4−1) = 3.
Show model answer and explanation
m/s²
Velocity change per second gives length/time².
Write in your own words. A guardian or teacher should review this response.
Show model answer and explanation
It systematically shifts readings rather than randomly varying between repeats.
Explain a consistent offset.
Write in your own words. A guardian or teacher should review this response.
Show model answer and explanation
They suggest precision unsupported by the measurement method.
Connect rounding to the evidence.
Show model answer and explanation
2
The residual is +2 in the y unit.
Write in your own words. A guardian or teacher should review this response.
Show model answer and explanation
Other factors, a limited range or a chosen transformation can also produce an apparently straight relationship.
Distinguish a useful fit from a proven mechanism.
Analyse supplied data
Invent and label six motion measurements, fit a simple line and discuss a limitation.
Review with a guardian or teacher
- Label invented data honestly.
- Show units and slope.
- Explain one reason a real experiment could differ.
Keep your work on paper or in a local file. This page does not upload it or automatically grade the project.
Teacher-led lessons, schedules and prices for this outline are upcoming. You can use any starter practice above now without booking.
Your next step
Solo practice works without an account. Sign in to save a practice record to your learner profile.
Keep practising
Exact lesson links and related activities are labelled separately. Return-to-course links retain your selected learning path.