DP Physics (last assessment 2024)

Question 18M.3.SL.TZ1.1

Date	May 2018	Marks available	[Maximum mark: 9]	Reference code	18M.3.SL.TZ1.1
Level	SL	Paper	3	Time zone	TZ1
Command term	Determine, Draw, Sketch, State, Write down	Question number	1	Adapted from	N/A

[Maximum mark: 9]

18M.3.SL.TZ1.1

A magnetized needle is oscillating on a string about a vertical axis in a horizontal magneticfield B. The time for 10 oscillations is recorded for different values of B.

M18/4/PHYSI/SP3/ENG/TZ1/01_01

The graph shows the variation with B of the time for 10 oscillations together with the uncertainties in the time measurements. The uncertainty in B is negligible.

(a)

Draw on the graph the line of best fit for the data.

[1]

Markscheme

smooth line, not kinked, passing through all the error bars.

[1 mark]

(b.i)

Write down the time taken for one oscillation when B = 0.005 T with its absolute uncertainty.

[1]

Markscheme

0.84 ± 0.03 «s»

Accept any value from the range: 0.81 to 0.87.

Accept uncertainty 0.03 OR 0.025.

[1 mark]

(b.ii)

A student forms a hypothesis that the period of one oscillation P is given by:

$P = \frac{K}{{\sqrt B }}$

where K is a constant.

Determine the value of K using the point for which B = 0.005 T.

State the uncertainty in K to an appropriate number of significant figures.

[3]

Markscheme

$K = \sqrt {0.005} \times 0.84 = 0.059$

« $\frac{{\Delta K}}{K} = \frac{{\Delta P}}{P}$ »

$\Delta K = \frac{{0.03}}{{0.84}} \times 0.0594 = 0.002$

«K =(0.059 ± 0.002)»

uncertainty given to 1sf

Allow ECF [3 max] if 10T is used.

Award [3] for BCA.

[3 marks]

(b.iii)

State the unit of K.

[1]

Markscheme

${\text{s}}{{\text{T}}^{\frac{1}{2}}}$

Accept $s\sqrt T$ or in words.

[1 mark]

(c)

The student plots a graph to show how P² varies with $\frac{1}{B}$ for the data.

Sketch the shape of the expected line of best fit on the axes below assuming that the relationship $P = \frac{K}{{\sqrt B }}$ is verified. You do not have to put numbers on the axes.