Boon Lay Prelim Ans

2024 Physics Prelim Paper 1 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. C B C D C C C C C C 11. 12. 13. 14. 15. 16. 17. 18. 19. 20. B D B B C C A B C B 21. 22. 23. 24. 25. 26. 27. 28. 29. 30. C C C B B D C D C B 31. 32. 33. 34. 35. 36. 37. 38. 39. 40. A C D A D D C B D A Paper 2 Qn Working Remarks 1a Volume of anchor = 3000 / 6900 = 0.435 m3 [1] Mass of seawater displaced = (3000/6900) × 1020 = 443.5 kg [1] 1b 1m – app scale 1m – correct arrows for 40 kN and 30 kN 1m – correct resultant force Allow for 1 labelling error.

2a P – straight upward slope Q – decreasing curve upwards R – increasing curve downwards, ends at the starting of Q. S – straight upward slope, gentler than P. P – [1m] Q & R [1m] S – [1m] 2b a = (-2 – 2)/4 = -1 m s-2 [1] 2c Acceleration is a vector – with magnitude and direction. [1] Even though the magnitude of speed is constant, the direction of travel is constantly changing. [1] Thus the robot is accelerating. 3a P = F / A = 400 N / 0.0003 m2 = 1333333 Pa = 1330000 Pa or 1.3 MPa. [1] 3b For a body in equilibrium, the sum of clockwise moments about a pivot is equal to the sum of counter clockwise moments [1] about the same pivot. [1] 3c 400 x 0.08 m = 32 N m (cw) [1] F1 x 0.02 m = 32 N m F1 = 1600 N [1] 3d When the brakes are applied, energy from the Kinetic store of the spinning wheel is converted into the energy in the Internal (heat) store of the wheel, brakes and surroundings. [1] 4a P = ρgh h = P / (ρg) = 101300 / (13546 × 10) =0.745 m 4b P = ρgh + 1 atm = 1030 × 10 × 18 + 101.3 kPa = 286700 Pa = 287 kPa 1m – fluid pressure 1m correct final answer

4c The bubble will expand as the pressure acting on it decreases. 4d As the diver ascends, the bubbles trapped in the body will expand since pressure decreases. The trapped bubbles might be stuck in narrow blood vessels or critical parts [1] that might rupture due to the expansion of the bubbles [1] Accept any reasonable answer. 5a Amount of thermal energy required to raise the temperature of 1 kg [1] of the sand by 1 °C. [1] 5b Energy used to heat up sand = msand × csand × ΔT = 1000 × 4000 × 3 = 12000000 J Energy used to heat up water = mwater × cwater × ΔTwater = mwater × 800 × ΔTwater Energy used to heat up water = energy used to heat up sand 12000000 = 10000 × 800 × ΔTwater ΔTwater = 1.5 °C 1m – calculating the energy required to said the temp of sand by 3 °C 1m – correct final answer 5c Since the sand is hotter than the sea[1], air above the sand rises due to its lowered density. [1] Denser air above the sea rushes in to take its place, forming sea breeze. [1] 6a Two light atomic nuclei combine to form one heavier atomic nucleus[1] and releases a huge amount of energy.[1] 6b Speed of light in vac = 3.0 × 108 m s-1 [1] d = 3.0