IB Physics HL S2.3 Concluding and evaluating Questions

SLSL HLHL

Practise IB Physics HL S2.3 by testing conclusions against uncertainty, model limits and competing explanations in extended investigations.

34 questions in this syllabus scope, with question parts counted together.

Exam points & syllabus

Exam points

Justify agreement with a reference by checking whether it lies inside the measured uncertainty interval, rather than comparing central values alone.
Use the fitted model parameter to support a conclusion: the stellar logarithmic slope is near 4, or the derived constant agrees with its accepted value.
Follow the heating energy: energy entering the surroundings or apparatus can make the sample’s calculated specific heat capacity too high.
Use the energy balance to find bias direction: losses lower inferred steam latent heat, while extra hot water raises inferred cube heat capacity.
Trace a constant zero offset through the analysis: shifting every current reading equally leaves the V-I slope and slope-derived internal resistance unchanged.
Limit a hypothesis to the range supported by the data, and convert reciprocal-axis limits before reporting the interval in time.
Explain why two selected points cannot establish a trend reliably; additional points help distinguish the model from scatter or an outlier.
Identify an error at the actual apparatus, such as pulley friction, slider thickness or neglected weight-tray mass; vague labels are insufficient.
For manual timing, connect the main uncertainty to the operator’s reaction when starting and stopping the stopwatch.
Expose assumptions behind a load estimate, including how the weight is shared and how the support’s contact shape is idealised.
Improve a diameter measurement with the same caliper by averaging repeats or measuring different diameters; zero the instrument to address an offset.

Covered syllabus points

S2.3.1—Concluding S2.3.2—Evaluating

Exam points

Compare the literature value with the full measured uncertainty interval: 0.24 Pa s lies within 0.25 ± 0.02 Pa s, supporting agreement.
For the stellar law test, use the fitted logarithmic slope near 4 to justify that the observed data support the stated T⁴ dependence.
Alternatively, compare the derived Stefan-Boltzmann constant with the accepted value and make the conclusion consistent with that comparison.

[Maximum number: 1]

A group of students is trying to determine the density and the viscosity of a liquid.

To determine the density, they use a balance to read the mass m of a sphere in air and immersed in the liquid.

They use a sphere of volume $V=1.827 \times 10^{-7} \mathrm{~m}^{3}$ .
The readings are $m_{\text {air }}=1.427 \mathrm{~g}$ in air and $m_{\text {immersed }}=1.208 \mathrm{~g}$ in the liquid.
The readings are different due to buoyancy. The buoyancy force $F_{\mathrm{b}}$ is given by

F_{\mathrm{b}}=\rho V g

where V is the volume of the sphere and $\rho$ is the density of the liquid.

The students search literature values and find the viscosity of this liquid to be 0.24 , when expressed in SI base units.

Suggest a conclusion reached by the students.

Exam points

Trace heating energy lost to the surroundings or apparatus, then explain why assigning all input energy to the sample overestimates its specific heat capacity.
A constant positive current zero error shifts all readings but leaves the V-I gradient unchanged, so the gradient-derived internal resistance is unchanged.
For the stated x = a/t hypothesis, convert the supported reciprocal-time range back to t; 0.025–0.04 s⁻¹ corresponds to 25–40 s.
Explain why two selected points cannot confirm a relationship: another point or a wider dataset is needed to distinguish the trend from scatter or an outlier.
Name a specific source of systematic error in the wire apparatus, such as pulley friction, slider thickness or neglected tray mass.
For manual single-period timing, identify reaction time in starting and stopping the stopwatch as the main stated error source.
In the steam experiment, heat lost to the surroundings reduces the energy received by the water and makes the inferred latent heat too low.
Hot water carried in with the heated cube adds energy not attributed to the cube, so the calculated cube specific heat capacity is too high.
State an assumption behind the airbag load estimate, such as uniform load sharing or the idealised contact shape at the bag ends.
Using the same caliper and sphere, take several diameter readings and average them, or measure across different diameters.
Correct the measurement procedure by zeroing the same caliper before use; this addresses its offset rather than reducing scatter by averaging.

[Maximum number: 1]

A student attaches one end of a copper wire to an oscillator operating at a fixed frequency. The other end of the wire passes over a pulley to weights that hang vertically. The first harmonic standing wave is established by using the slider to change the length of the wire. The procedure is repeated for different weights.

The mass m of the weights and the wavelength $\lambda$ of the wave are related by

m=\frac{\mu f^{2}}{g} \lambda^{2}

where $\mu$ is a constant, f is the frequency of the wave and $g=9.8 \mathrm{~ms}^{-2}$ .

The graph shows the data obtained by the student, plotted to show the variation of m with $\lambda^{2}$ .

Suggest a possible reason for the systematic error.

Question 1

Question 1