EJC 2024 J2 H2 PRELIM Answers P4

©EJC 2024 9749/04/J2H2Prelim/2024 [Turn over EUNOIA JUNIOR COLLEGE JC2 PRELIMINARY EXAMINATIONS 2024 9749 PHYSICS MARK SCHEME Paper 4 – Practical Qns Answer Marks 1bi • Correct precision of 0.1 cm and corresponding unit for 1L • Repeated readings for 1L 1 • Correct precision of 0.1 cm and corresponding unit for 1x 1 1bii • Show ΔL0 < ΔL1 • Δx1 > 4 mm (ΔL0 < ΔL1) • Correct calculation of percentage uncertainty • 2 s.f. for final answer 1 no marks if not shown 1 1biii • Correct precision of 0.1 cm and corresponding unit for 2x • x2 > x1 1 1ci •  correctly calculated without units accept 2 or 3 s.f. 1 1cii Either • Plot a graph of 2x against 1x where the gradient is 2e and the y-intercept is zero. • ( ) = 1 ln gradient2 1 1 Or • Plot a graph of 2ln x against 1ln x where the gradient is 1 and the y-intercept is 2 • ( ) = 1 vertical intercept2 1ciii • If the pipe is frictionless, =12xx (as the spring will retract back to an extension of 1x after being stretched further). 1 • Hence, ( ) ( )==21ln ln 1 0xx and this implies  = 0 . 1 Total 10

2 ©EJC 2024 9749/04/J2H2Prelim/2024 Qns Answer Marks 2ai • Correct precision of 0.1 cm and corresponding unit for L and r • Repeated readings for L and r • Repeated readings for t in 2 d.p. • t > 10 s , 45.0 cm  L  55.0 cm • Correct calculation, number of d.p. / s.f. and unit for <t>, T 1 2aii • 1 cm ≤ ∆r ≤ 3 cm • Correct calculation of percentage uncertainty to 2 s.f. • Percentage uncertainty 10% 1 2b • 4 sets of readings without assistance • Correct trend: as L decreases, T decreases 1 • Correct column headings with correct units. Must include column for no. of oscillations & <t> • Repeated readings for t • Table must not be broken up into 2 separate tables 1 • Consistent and correct d.p. for raw data in each column • Correct s.f./d.p. for processed data • Correct calculation, s.f. for <t>, T • t > 10 s , 45.0 cm  L  55.0 cm 1 2c • Statement of graph to be plotted must be provided. • All observations must be plotted to an accuracy to half a small square. • Scale chosen is such that the plotted points occupy at least half the graph grid in both directions. Awkward scales (e.g. 1:3) are not allowed. • Axes are labelled no more than 4 cm apart, but no less than 2 cm apart • Best-fit line drawn 1 • Coordinates used to find gradient are read to the accuracy of half small square. • The coordinates used must be more than half the length of the line away. • Correct calculation of gradient to 3 s.f. 1 • A determined correctly with correct unit to 3 s.f. 1 2d • g determined correctly in m s−2 to 3 s.f. 1 2e • Percentage difference calculated correctly and given to 2 s.f. 1 • Compare percentage difference in g and percentage uncertainty in r • Draw correct conclusion depends on candidate’s experimental results. 1 2f • Expected line clearly labelled as M • Larger A → steeper gradient • Larger B → lower y-intercept (larger negative value) * If new line’s gradient and y-intercept not clearly discernable, may award marks if student annotate correctly 1 Total 12

3 ©EJC 2024 9749/04/J2H2Prelim/2024 [Turn over Qns Answer Marks 3ai • 5 sets of readings without assistance • Correct trend: as I increases, V increases 1 • 2 d.p. for I in mA • 2 d.p. for V in V 1 3aii • All observations must be plotted to an accuracy to half a small square. • Scale chosen is such that the plotted points occupy at least half the graph grid in y-direction. Awkward scales (e.g. 1:3) are not allowed. • Axes are labelled no more than 4 cm apart, but no less than 2 cm apart 1 • Even number of data points on each side of best-fit curve. If anomalous data present, it must be circled and labelled. 1 3aiii • As current increases, LED resistance decreases 1 3bi • Repeated readings for minV in 2 d.p. in volts • 1.5 V  minV  1.75 V 1 3bii • Correct explanation of use of 22  resistor: to limit current passing through the LED 1

4 ©EJC 2024 9749/04/J2H2Prelim/2024 Qns Answer Marks 3ci • 5 sets of readings for 5 different LED colours without assistance • Correct trend: as frequency increases, minV increases 1 • Repeated readings for minV in 2 d.p. in volts 1 3ciii Possible source of uncertainty: 1. Difficulty in judging when LED “just turn on” based on visual inspection, thus affecting the measurement of minV 2. Difficulty in getting a precise value of minV as a slight shift of the jockey on the resistance wire produces a large change in the voltmeter reading. 1 (B/BFL) 3cii Linearising equation and statement. • Correct linearization with statement clearly presented 1 Gradient • The hypotenuse of the gradient triangle must be at least half the length of the drawn line. Both read-offs must be accurate to half a small square. • Gradient triangle must occupy at least half the graph grid in both x- and y- directions. • Correct calculation of gradient 1 Determine constant Correct determination of h with units 1 Axes • Scale chosen is such that the plotted points occupy at least half the graph grid in x and y-direction. Awkward scales (e.g. 1:3) are not allowed. • Axes are labelled no more than 4 cm apart, but no less than 2 cm apart 1 (S) Plotting of points • All observations must be plotted to an accuracy to half a small square. 1 (P) Line of best-fit • Best fit line drawn with equal distribution of data points on either side There must be an even distribution of points either side of the line along the full length. Line must not be kinked. • Anomalous point must be circled and labelled. 1 (B/BFL)

5 ©EJC 2024 9749/04/J2H2Prelim/2024 [Turn over Qns Answer Marks 3d In general, the plan should be written such that the marker can carry out the experiment successfully by following your planning. The procedure should be in sequential logical order. • Diagram showing workable setup: - circuit plus position of light sensor and light meter 1 (d) • Method to vary and measure independent variable: - measurement of current I, V using ammeter & voltmeter - computation of input power P 1 (I) • Method to vary and measure dependent variable: - measurement of light intensity L with light sensor connected to light meter or using light intensity meter or lux meter. 1 (D) • Method to keep control variable constant: - distance and direction of light sensor to LED kept constant - use same colour LED 1 (C) • Analysis: - details on expected graph to be plotted, e.g P against 2L - relation valid if straight-line graph passing through origin obtained and mentioned of gradient 1 (A) • Precaution (any one): - conduct experiment in dark room - look at LED through a hollow tube to cut out ambient light 1 (P) Total 22

6 ©EJC 2024 9749/04/J2H2Prelim/2024 Q4 Diagram P Workable arrangement including • with speaker connected to signal generator at one end of tube, • sound sensor / microphone at other end connected to datalogger / CRO • apparatus held in place, and not hanging in mid air supernaturally. D1 Procedure P Independent Variable(s) Measure length of tube L with metre rule B1 Measure inner diameter d with internal jaw of the vernier calliper. B2 Dependent Variable Method to measure f: • increase f on signal generator from zero to get first harmonics when sound intensity reaches maximum the first time. • determine period T from CRO / data logger, and use formula f = 1/T C1 C2 Run #1: Method to maintain L + Method to vary d Vary d by using tubes of the same length but different inner diameters. Measure f for different d. R1 Run #2: Method to maintain d + Method to vary L. Vary L by using tubes of same inner diameter but different le