IB Physics SL Mathematics
Review IB Physics mathematics through SI units, dimensional checks, graph gradients and areas, uncertainty propagation and significant-figure decisions.
- Syllabus
- First assessment 2025
- Topic
- S1.3
- Level
- SL
Review IB Physics mathematics through SI units, dimensional checks, graph gradients and areas, uncertainty propagation and significant-figure decisions.
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 .
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 θi and refraction θr at P and record them on a table.

Complete the table.

0.755
Accept only 0.755. Answer must be
quoted to 3 sf .
[1]
They plot a graph of the variation with the sine of θi of the sine of θr.
They add uncertainty bars for sinθr for the first and last data point and draw the best-fit line.

Determine the gradient of the students' best-fit line.
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 Δx≥0.3
[2]
Draw on the students' graph the line of maximum gradient.
draw max from lower end of lower error bar to upper end of upper error bar
[1]
A glider is an aircraft with no engine. To be launched, a glider is uniformly accelerated from rest by a cable pulled by a motor that exerts a horizontal force on the glider throughout the launch.

At a particular instant in the flight the glider is losing 1.00 m of vertical height for every 6.00 m that it goes forward horizontally. At this instant, the horizontal speed of the glider is 12.5 m s−1. Calculate the velocity of the glider. Give your answer to an appropriate number of significant figures.
any speed and any direction quoted together as the answer quotes their answer(s) to 3 significant figures
speed =12.7 m s−1 or direction =9.46∘ or 0.165 rad «below the horizontal» or gradient of −61
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 ±1 mm.

The students systematically increase the pressure and calculate d.

State the absolute uncertainty of d.
«Addition of absolute uncertainties ± » 2 mm
Accept 0.002
The students suggest the following relationship between d and P :
where k is a constant.
To verify the relationship, the variation of d with P is plotted.
One data point is missing.

The percentage uncertainty in P is ±8%. Determine the uncertainty for P when d=33 mm and draw the uncertainty bar for this data point on the graph.
Alternative 1
«Uncertainty in P is» 21×0.08=±4%±4%×500=±20
Uncertainty bar plotted correctly
Alternative 2
250000+20000−250000−200000.08×250000=20000=±20
Uncertainty bar plotted correctly
The SI units of k can be expressed as kg−21 mx sy. Determine the values of x and y.
x = 3/2 and y = 1.