2024 MSH SC(PHY) PRELIM ANS

MARIS STELLA HIGH SCHOOL SECONDARY 4 SCIENCE(PHYSICS) 2024 PRELIMINARY EXAMINATION Deduction of 1 m per occurrence (cap of 1 m per type of error for the entire paper): • Incorrect or unclear presentation (P) or Incorrect or missing formula (F) • Incorrect or missing units (U) • Incorrect no. of significant figures (SF) Paper 1 [20 marks] 1 2 3 4 5 6 7 8 9 10 D A D A A C A D A D 11 12 13 14 15 16 17 18 19 20 C C B B B B A C B C Paper 2 Section A [55 marks] Answer all the questions in this section. Qn Mark Scheme Marks 1 (a) Best fit curve from t = 0 s to t = 26 s [B1] Straight line through all 3 points from t = 26 s to t = 30 s [B1] (b) (i) 𝐸𝑘 = 1 2 𝑚𝑣2 = 1 2 (46 𝑘𝑔)(15.2 𝑚 𝑠⁄ )2 = 5313.92 𝐽 = 5300 𝐽 (𝑡𝑜 2 𝑠. 𝑓. ) C1 A1 (ii) 𝑎 = 𝑔𝑟𝑎𝑑𝑖𝑒𝑛𝑡 𝑜𝑓 𝑣 − 𝑡 𝑔𝑟𝑎𝑝ℎ = 0 − 15.2 30 − 26 = −3.8 𝑚 𝑠2⁄ deceleration = 3.8 m/s2 C1 A1 (iii) 𝐹 = 𝑚𝑎 = (46 + 9 𝑘𝑔)(3.8 𝑚 𝑠2⁄ ) = 209 𝑁 = 210 𝑁 (𝑡𝑜 2 𝑠. 𝑓. ) C1 A1

2 (iii) Energy is transferred from the kinetic store and gravitational potential store of the child and sledge to internal energy of surroundings through a mechanical pathway. B1 B1 2 (a) (i) 𝜌 = 𝑚 𝑉 1000 𝑘𝑔 𝑚3⁄ = 𝑚 2.5 × 10−4 × 0.12 m3 m = 0.030 kg (F) C1 A1 (ii) 𝑃 = 𝐹 𝐴 = (0.030 𝑘𝑔 × 10 𝑁 𝑘𝑔⁄ ) 2.5 × 10−4 𝑚2 = 1200 𝑁 𝑚2⁄ (F) C1 A1 (iii) 𝑃 = 𝐹 𝐴 1200 𝑁 𝑚2⁄ = (𝜌 × 2.5 × 10−4 × 0.15 m3 × 10 𝑁 𝑘𝑔⁄ ) 2.5 × 10−4 𝑚2 𝜌 = 800 𝑘𝑔 𝑚3⁄ C1 A1 (c) Turn the clamp so that the U-tube is directly above the base of the retort stand OR Lower the clamp so that the centre of gravity of the set up is lowered. B1 3 (a) (i) newton-meter OR spring balance (ii) measuring tape B1 B1 (b) (i) The principle of moments states that when a body is in equilibrium, the sum of clockwise moments about a pivot is equal to the sum of anticlockwise moments about the same pivot B1 B1 (ii) In equilibrium, taking moments about the pivot, Sum of clockwise moments = sum of anti-clockwise moments 𝐹 × 5.000 𝑚 = 52.0 𝑁 × 0.250 𝑚 𝐹 = 2.6 𝑁 (P) C1 A1 4 (a) Heat is transferred via conduction Copper is a good conductor of heat as it has free electrons. B1 B1 (b) The water around the copper pipe is cooled, contracts and becomes denser, allowing it to sink to the bottom. Warmer water rises to take its place forming convection currents. Since water is a poor conductor of heat, t his cools the water below efficiently allowing less dense room temperature water to remain above. B1 B1 (c) As temperature of the liquid decreases, the molecules lose average kinetic energy, they slide over one another at lower speeds. B1 B1 5 (a) (i) 340 m/s A1 (ii) 𝑣 = 𝑓𝜆 340 𝑚 𝑠⁄ = 485 𝐻𝑧 × 𝜆 𝜆 = 0.70 𝑚 (F) E1 A1 (iii) Sound waves of different frequencies travel at the same speed in the same medium. B1

3 (b) As speed of sound in metal is greater than in air, the sound will take a shorter time to travel the same distance and hence timer will have a smaller