IB Physics SL S Skills in Physics Questions

Practise IB Physics SL skills by handling units, uncertainties, graphs, instruments and measurements, then interpreting evidence in physical contexts.

Exam points

Choose instruments, variables and procedures, then record measurements with correct units, significant figures and uncertainties.
Apply algebra, trigonometry, graph methods, proportional reasoning and dimensional checks to physical calculations.
Design reproducible investigations with research questions, hypotheses, controls, variables, ranges, repeats and risk management.
Process data, assess trends and uncertainty, draw justified conclusions and evaluate errors, limitations and realistic improvements.

Covered syllabus points

S1.1 Experimental techniques S1.2 Technology S1.3 Mathematics S2.1 Exploring and designing S2.2 Collecting and processing data S2.3 Concluding and evaluating

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Study S Skills in Physics conceptsOpen the corresponding Concept lesson for explanations, examples and exam connections.

[Maximum number: 2]

This question is about mobile phones.

The number of mobile phones has grown rapidly in recent years. Discuss environmental issues associated with this rapid increase.

[Maximum number: 5]

A group of students is investigating refraction in a semi-circular glass block.

Light from a ray box enters the curved side of the block. The light passes through the block and leaves, refracted, at P .

(a)

The students vary the position of the ray box to obtain data to determine the refractive index of the glass. They use a protractor to collect values for the angles of incidence $\theta_{i}$ and refraction $\theta_{r}$ at P and record them on a table.

[ 2 ]

(i)

One of their measurements is shown. State $\theta_{r}$ for this measurement.

[ 1 ]

$\theta_{r}=49$

Marking guidance:

Accept correct answer only

[1]

(ii)

Complete the table.

[ 1 ]

(b)

They plot a graph of the variation with the sine of $\theta_{i}$ of the sine of $\theta_{r}$ .
They add uncertainty bars for $\sin \theta_{r}$ for the first and last data point and draw the best-fit line.

[ 3 ]

(i)

Determine the gradient of the students' best-fit line.

[ 2 ]

use two points from the line that use more than half the line of best fit
gradient =1.5

Marking guidance:

Allow (implicit) use of the origin.

Look for $\Delta \mathrm{x} \geq 0.3$

[2]

(ii)

Draw on the students' graph the line of maximum gradient.

[ 1 ]

[Maximum number: 4]

A student investigates whether the Stefan-Boltzmann law, $L=4 \pi \sigma R^{2} T^{4}$ , applies to stars.
L= luminosity of the star, in W
$\sigma=$ Stefan-Boltzmann constant
R= radius of the star, in m
T= surface temperature of the star, in K
To verify the law, they obtain values from databases and manipulate the data as shown.

(a)

Complete the table with the missing values for Polaris B.

The student plots the variation with $\log T$ of $\log \left(\frac{L}{R^{2}}\right)$ and draws the line of best fit.

The student uses a GDC (graphical display calculator) to determine the equation of the line of best fit as y=3.99 x-6.15.

[ 2 ]

$1.63 \times 10^{9}$

and 3.84

If they use more or fewer than 3 SF,

max [1].

(b)

Outline a conclusion for the investigation.

[ 1 ]

ALTERNATIVE 1

the linear graph suggests that SB applies to stars

ALTERNATIVE 2

the «accurate » calculation of $\sigma$ from the data suggests that SB applies to stars

ALTERNATIVE 3

« if 2c has a value of $\sigma$ that is not accurate » the calculation of the $\sigma$ from the data suggests SB does not apply to stars

(c)

Suggest a possible improvement of the investigation, related to the range of the surface temperatures of the stars selected.

[ 1 ]

[Maximum number: 13]

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.

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 $\pm 1 \mathrm{~mm}$ .

(a)

Describe one consideration that must be made when placing the ruler to ensure that the length of the nail remaining above the surface of the wood is measured accurately.

[ 1 ]

(b)

The students systematically increase the pressure and calculate d.

[ 5 ]

(i)

State one variable that needs to be controlled when collecting the data.

[ 1 ]

(ii)

Outline how the students determined the value of d.

[ 1 ]

(iii)

State the absolute uncertainty of d.

[ 1 ]

«Addition of absolute uncertainties $\pm$ » 2 mm

Accept 0.002

(iv)

By using two sets of data in the table, show that the relationship between d and P is not directly proportional.

[ 2 ]

(c)

The students suggest the following relationship between d and P :

d=k \sqrt{P}

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

[ 6 ]

(i)

Determine the coordinates of the missing point using the original data set and plot it on the graph.

[ 1 ]

Correctly plotted ( $447 \pm 3,30$ )

(ii)

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

[ 3 ]

Alternative 1

«Uncertainty in $\sqrt{P}$ is» $\frac{1}{2} \times 0.08= \pm 4 \%$ $\pm 4 \% \times 500= \pm 20$

Uncertainty bar plotted correctly

Alternative 2
$\frac{0.08 \times 250000=20000 \quad }{\sqrt{250000+20000}-\sqrt{250000-20000}}= \pm 20$

Uncertainty bar plotted correctly

(iii)

The SI units of k can be expressed as $\mathrm{kg}^{-\frac{1}{2}} \mathrm{~m}^{x} \mathrm{~s}^{y}$ . Determine the values of x and y.

[ 2 ]

(d)

The students collect only one value of d for each value of P. Suggest why this is a poor method.

[ 1 ]

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