Broadrick Prelim P3 Ans

2024 4E Prelim Paper 3 Practical Test Marking Scheme Question 1 (a) l = 2.1 cm d = 1.6 cm [1] [1] (b) m = 5.3 g n = 30 N = 34 [1] [1] (c) D = 0.0700 cm [1] (d)(i) (d)(ii) (d)(iii) L = 171 cm V = 0.658 cm3 ρ = 8.06 g / cm3 [1] [1] [1] (e) Source of error: 1. Precision of the ruler is only 0.1 cm 2. There is a portion of wire between the coiled part and the 2 turns on each end that is not accounted for. Effect on calculated value of ρ: 1. Value of V is overestimated, so calculated value of ρ may be smaller than the actual value of ρ. 2. Value of V is underestimated, so calculated value of ρ may be larger than the actual value of ρ. [1] [1] Total marks: 10 Question 2 (a) θ = (results to be updated on practical dry run) [1] (b) r = (results to be updated on practical dry run) [1] (c) T = (results to be updated on practical dry run) [1] (d) Planning mark allocation: Variables – 1m, 1m Performing experiments (starting value of independent variable, measuring dependent variable & 5 more values to obtain more readings, table) – 1m, 1m Statements and sketch of graphs – 1m, 1m How to achieve accurate results – 1m [7]

Plan 1 Independent variable: distance that the piece of Blu-Tack moves d Dependent variable: time taken for the piece of Blu-Tack to reach the bottom of the cylinder T Control variable: type of oil, radius of the piece of Blu-Tack r. 1. Fill the measuring cylinder such that the height of the column of oil is 5 cm so that the distance that the piece of Blu-Tack moves is d = 5 cm. 2. Place the piece of Blu-Tack at the top of the oil as shown in Fig. 2.1. Use the string to hold the piece of Blu-Tack so that it just touches the surface of the oil in the measuring cylinder. Release the string and start the stop-watch. Stop the stopwatch when the piece of Blu-Tack reaches the bottom of the measuring cylinder. Record the time T1 taken for the piece of Blu-Tack to reach the bottom of the cylinder. 3. Repeat step 2 two more times to obtain T2 and T3 and find the average value Tavg to achieve accurate results. 4. Repeat steps 1 – 3 for five further values of d (8 cm, 10 cm, 12 cm, 15 cm, 18 cm). 5. Record the values of d, T1, T2, T3, and Tavg in a table. 6. Plot the graph of Tavg against d. If the suggested relationship is correct, we will obtain the following graph: The graph should be a straight line passing through the origin if T is directly proportional to d. [1] [1] [1] [1] T / s d/ cm 0

Plan 2 Independent variable: radius of the piece of Blu-Tack r Dependent variable: time taken for the piece of Blu-Tack to reach the bottom of the cylinder T Control variable: type of oil, distance that the piece of Blu-Tack moves d 1. Roll a ball of Blu-Tack and attach a string to it such that the radius of the piece of Blue-Tack is r = 1 cm. 2. Place the piece of Blu-Tack at the top of the oil as shown in Fig. 2.1. Use the string to hold the piece of Blu-Tack so that it just touches the surface of the oil in the measuring cylinder. Release the string and start the stop-watch. Stop the stopwatch when the piece of Blu-Tack reaches the bottom of the measuring cylinder. Record the time T1 taken for the piece of Blu-Tack to reach the bottom of the cylinder. 3. Repeat step 2 two more times to obtain T2 and T3 and find the average value Tavg to achieve accurate results. 4. Repeat steps 1 – 3 for five further values of r (1.2 cm, 1.4 cm, 1.6 cm, 1.8 cm, 2 cm). 5. Record the values of r, 1 / r2, T1, T2, T3, and Tavg in a table. 6. Plot the graph of Tavg against 1 / r2. If the suggested relationship is correct, we will obtain the following graph: The graph should be a straight line passing through the origin if T is directly proportional to 1 / r2. [1] [1] [1] Total marks: 10 T / s 1 / r2 / 1 / cm2 0

Question 3 (ai) (aii) V1 = 1.10 V I1 = 0.14 A R = 7.86 Ω P = 0.154 W [1] [1] [1] [1] (b) L / cm V / V I / A R / Ω P / W 100.0 1.10 0.14 7.86 0.154 80.0 1.30 0.15 8.67 0.195 60.0 1.60 0.16 10.0 0.256 40.0 1.90 0.18 10.6 0.342 20.0 2.30 0.20 11.5 0.460 10.0 2.60 0.21 12.4 0.546 5.0 2.80 0.22 12.7 0.616 Heading and units in heading, at least 6 readings, no units in table [5] [1] (c) Graph Scale – at least half the grid provided, consistent scale [1] Lines – curved line of best fit line [1] Axes – labelled with title/ unit, starting values clearly stated [1] Points – plotted accurately [1] [4] (d) Tangent drawn at L = 60.0 cm G = - 0.00356 W / cm [1] [1] (e) Trend: The graph of P against L is a curve. As the value of L increases, the value of P decreases at a decreasing rate, i.e. the gradient of the curve gets gentler as L increases. P is inversely proportional to L. [1] [1] (f) Sources of error: 1. There are kinks in the wire and the wire cannot be straightened on the ruler, affecting the measurement of length L. 2. The wire and the circuit components become hot after some time and resistance increases, affecting the voltmeter and ammeter readings. 3. The voltmeter and ammeter readings fluctuate, making it difficult to record an exact value of V and I. [1] [1] Total marks: 20

End of Marking Scheme