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IB Physics SL S1.3.4 Uncertainties Questions

Analyse SL random and systematic uncertainties, combining percentage uncertainties and reporting measurements with appropriate precision.

Syllabus
First assessment 2025
Course
Physics SL
Level
SL

Exam points

  • distinguish random uncertainty from systematic uncertainty using patterns, spread and displacement from a target or accepted value
  • combine percentage uncertainties in products, quotients and powers, including uncertainty in g from l and t
  • report uncertainty and measured values with appropriate significant figures and explain how uncertainty affects a conclusion

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Study S1.3.4—Uncertainties conceptsOpen the corresponding Concept lesson for explanations, examples and exam connections.

IB Physics SL S1.3.4 Uncertainties Questions question 1

[Maximum number: 4]

A group of students uses pressurized air to move a piston that forces a nail into a block of wood. A gauge is used to measure the pressure P of compressed air above atmospheric pressure. The nail enters the wood perpendicular to its surface.

Figure for Question IB Physics SL S1.3.4 Uncertainties Questions question 1 — IB Physics SL

The students use a ruler to measure the length of the nail which remains above the surface of the wood as shown. The depth of the nail inside the wood is d. All necessary length measurements are recorded using a ruler with uncertainty ±1 mm\pm 1 \mathrm{~mm}.

Figure for Question IB Physics SL S1.3.4 Uncertainties Questions question 1 — IB Physics SL

Question (a)

(a)

The students systematically increase the pressure and calculate d.

Table for Question (a) — IB Physics SL
[ 1 ]

Question (i)

(i)

State the absolute uncertainty of d.

[ 1 ]

Question (b)

(b)

The students suggest the following relationship between d and P :

d=kPd=k \sqrt{P}

where k is a constant.
To verify the relationship, the variation of d with P\sqrt{P} is plotted.
One data point is missing.

Figure for Question (b) — IB Physics SL
[ 3 ]

Question (i)

(i)

The percentage uncertainty in P is ±8%\pm 8 \%. Determine the uncertainty for P\sqrt{P} when d=33 mmd=33 \mathrm{~mm} and draw the uncertainty bar for this data point on the graph.

[ 3 ]
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