Edexcel A-Level Physics Precision, Accuracy and Sensitivity

Review precision, accuracy and sensitivity in Edexcel A-Level Physics through uncertainty limits, repeat ranges and light-gate measurement decisions.

Exam points

compare precision using the spread or range of repeated readings with the same mean value
judge accuracy by checking whether an accepted value lies within an uncertainty limit
discuss light-gate or data-logger changes using reaction time, parallax and timing uncertainty

[Maximum number: 6]

A student used the apparatus shown to investigate the time taken for a hollow cylinder to roll down a ramp.

Figure for Question 6.5.6 - Precision, accuracy and sensitivity question 1 — Edexcel A-Level Physics A2

(a)

Two students each carried out this procedure for another value of $\Delta h$ . They recorded the following times for the same value of $\Delta h$ .

Table for Question (a) — Edexcel A-Level Physics A2

Compare the accuracy and precision of the data that each student collected.

[ 4 ]

(b)

The relationship between t and the acceleration of free fall g is given by

t² = 4s² / (gΔh)

where s is the distance along the ramp between the start line and the finish line.
The student recorded the following values.

t = 2.44 s ± 0.04 s
s = 80.0 cm ± 0.1 cm
Δh = 43 mm ± 1 mm

[ 2 ]

(i)

Deduce whether the value of g is accurate.

[ 2 ]

The lower limit is $10.0(100-5.9)/100=9.4\,\mathrm{m\,s^{-2}}$ . The accepted value $9.81\,\mathrm{m\,s^{-2}}$ lies within the uncertainty range, so the result is accurate. Equivalently, the percentage difference $1.9\%$ is less than the percentage uncertainty $5.9\%$ .

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6.5.6 - Precision, accuracy and sensitivity question 1

Question (a)

Question (b)

Question (i)