9702 · P5
Paper 5 Planning, Analysis & Evaluation — FAQ
Frequently asked questions for 9702 Paper 5 Planning, Analysis & Evaluation. Direct answers first, then deeper explanation — then practise with marking.
Do I have to draw error bars for both the x and y axes?
No, this is a common misconception. For Cambridge A-Level Physics, you are almost always expected to calculate and draw error bars for the y-axis quantity only. The uncertainty in the independent variable (x-axis) is usually considered negligible in comparison. Only draw x-axis error bars if the question explicitly instructs you to or if their uncertainty is unusually large and significant.
For the planning question, how detailed does my diagram need to be?
Your diagram must be a clear, labelled line drawing showing the essential apparatus in its correct arrangement for the experiment. It does not need to be artistic, but it must be functional and unambiguous. All key components mentioned in your method must be present and labelled (e.g., power supply, voltmeter, ammeter, variable resistor, test wire, metre rule). If a circuit is involved, a separate, standard circuit diagram is often the clearest approach.
My Worst Acceptable Line doesn't go through all the error bars. What have I done wrong?
The WAL, by definition, must pass through every single error bar. If yours does not, it is not a valid 'worst' line and will not score marks. The most common error is drawing a line that is simply 'a bit steeper' than the best fit line. The correct technique is to 'pivot' your ruler on an extreme of an error bar at one end of the graph (e.g., the very top of the first error bar) and rotate it until it just touches an extreme of an error bar at the other end (e.g., the very bottom of the last error bar). This ensures it cuts through all error bars in between.