YTSS 2025 Prelims ANSWER SCHEME

1 YTSS 4E PHYSICS PRELIM ANS KEY Ques Ans Ques Ans Ques Ans Ques Ans 1 D 11 C 21 C 31 D 2 C 12 A 22 B 32 D 3 B 13 D 23 B 33 D 4 C 14 A 24 B 34 C 5 A 15 A 25 B 35 A 6 C 16 D 26 D 36 D 7 C 17 C 27 A 37 D 8 A 18 D 28 A 38 A 9 A 19 B 29 C 39 D 10 B 20 A 30 D 40 A To award for answers based on intermediate working so long physics concept shown is correct / logical -1 max for sf (per question) -1 max for unit (per question) 1 (a) 4.5 cm [1] (b) Digital calipers or vernier calipers [1] Digital micrometer is not accepted. (c) Do not agree with student B. [1] The instrument could be more precise but not necessarily accurate. [1] Award zero if agree with student B 2 (ai) Acceleration = (8.8 – 0) / (3.0 – 2.1) [1] a = 9.8 m/s2 [1] Award 1m for any correct value of time or velocity (aii) Initial height = 0.5 x 10.8 x 1.1 [1] = 5.9 m [1] Award 1m if show idea of area of triangle AND at least time or velocity is correct. (aiii) new max height = 0.5 x 8.8 x 0.9 = 4.0 m [1] displacement = 5.9 – 4.0 = 1.9 m [1] If new max height is incorrect, max 1m for showing difference in heights. (b) The gradient of the graph is constant, showing that air resistance does not affect the acceleration. Do not just accept acc is constant [1] Ans MUST have reference to fig. 3 (ai) It states that, The sum of CW moments about a pivot is equal to the sum of ACW moments about the same pivot [1]

2 For a system/object to be in equilibrium [1] (aii) F x 1.5 = 150 x 0.75 [1] F = 75 N [1] Award max 1m if ans wrong but one side of eqn correct. (b) There is a normal contact force upwards on the pivot. Therefore, weight will balance out with normal contact force AND the force F. [1] [1] 4 (ai) Pdiff = 1000 x 10 x 0.09 m [1] = 900 Pa [1] Max 1m if didn’t convert cm to m. (aii) New height difference = 0.10 m Hence, right side must rise by 0.05 cm, left side drops by 0.05 cm. Right side, 25.5 cm, left side, 15.5 cm Accept RHS, 26, LHS, 16 ONLY if 25.5 and 15.5 is shown in working [1] [1] (b) It cannot (give BOD to student even if explanation wrong) The pressure due to water (or oil) is not enough to balance out the pressure due to gas (or manages to explain that most of the pressure balance comes from Patm) [1] [1] 5 (a) It is a disturbance in which the direction of vibration of particles is perpendicular to the direction of wave travel. [1] Do not accept move perpendicular (b) The wave travels 1.0 cm in 2 seconds. Hence, speed = 0.50 cm/s [1] (c) Wavelength = 6.0 cm Speed = 0.50 cm/s Period = 6.0 / 0.50 = 12 s [1] [1] (d) Y is directly above X, displacement of 2.0 cm [1] 6 (a) Sound that cannot be heard