Test Qgh = C + Df³: vary the blade frequency f with a fan, measure the mass of liquid pumped per second, plot Q against f³, then get C from the y-intercept and D from the gradient. Read the question, write your own plan on paper, then build it below box by box and see how many of the 15 marks it earns. The worked example shows a full-mark plan with the mark scheme point each line scores.
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Name the independent and dependent variables (the quantity you change and the one you measure) and say which quantity in the relationship is kept constant, in so many words.
A labelled diagram of an arrangement that would work, and how each quantity in the relationship is measured: the instrument and the technique.
The graph to plot (both axes named), “the relationship is valid if” it is a straight line (through the origin, or with a stated gradient), and the constant made the subject of an equation using the gradient or intercept.
Marked from a list of points specific to this experiment: a precaution tied to a real hazard here, how to measure the other quantities, repeats and averages, and techniques that make each reading more reliable.
The question on this page is rephrased from a Cambridge International past paper for teaching. The figures, wording of the workout and the worked example are our own; the marking follows the published mark scheme. The original question paper is available from Cambridge.