2024 CHR Physics Prelim ANS

CHR SEC 4 EXP SCIENCE PHYSICS (5086) PRELIM 2024 PROPOSED MARKING SCHEME (FOR TEACHERS ONLY) RESTRICTED 1 Paper 1: Q A Q A Q A Q A Q A Q A Q A Q A 1 A 6 C 11 D 16 C 21 B 26 C 31 B 36 A 2 C 7 D 12 B 17 D 22 A 27 D 32 B 37 B 3 B 8 C 13 B 18 C 23 D 28 B 33 A 38 C 4 B 9 B 14 A 19 D 24 C 29 B 34 D 39 D 5 A 10 D 15 C 20 B 25 A 30 D 35 B 40 C Q Suggested Answer-Concept-Explanation (ACE approach) Marks 1 Answer (A): A Concept (C): Range and precision of instrument Explanation (E): Internal diameter of test-tube -digital calipers Thickness of wire – digital micrometer screw gauge [1] 2 A: C C: Common examples of scalar and vector quantities E: Four vector quantities: i. force, ii. displacement, iii. acceleration, iv. change of velocity [1] 3 A: B Distance travelled = area under speed-time graph [C] = [½ (25 + 20) (10)] + ½ (10) (10) [E] = 275 m [A] Average speed = total distance travelled / total time taken [C] = 275 / 25 [E] = 11 m/s [A] [1] 4 A: B C: Area under speed-time graph =3.0 ½ (5) (t ) = 3.0 [E] t = 1.2 s [A] [1] t speed (m/s) 5.0 t/s

CHR SEC 4 EXP SCIENCE PHYSICS (5086) PRELIM 2024 PROPOSED MARKING SCHEME (FOR TEACHERS ONLY) RESTRICTED 2 5 A: A C: Acceleration of free-fall near earth surface, disregard air resistance E: Constant acceleration [1] 6 A: C C: inertia E: mass is the property that resists change in motion of the body [1] 7 A: D C: Resultant force F = ma FE - 45 - 5 = (4500 + 1000) (0.10) [E] FE = 600 N FBD: Resultant force F = ma [C] T -5 = 1000 (0.1) [E]  T = 105 N Use FBD on the engine to check. [1] 8 A: C Using Principle of Moments, taking moments about P, Sum of CWM = Sum of ACWM [C] F x 0.75 = W x 0.25 [E] W = 3F  F = 1/3 W Total upward force = Total downward force [C] F + P = W P = W – F = W - 1/3 W = 2/3 W Alternatively, take moments about 100 cm mark to arrive at P = 2/3 W [1] 9 A: B; Object with broadest base, lowest CG [E] gives the greatest stability [C] [1] 5 N 45 N T 5N

CHR SEC 4 EXP SCIENCE PHYSICS (5086) PRELIM 2024 PROPOSED MARKING SCHEME (FOR TEACHERS ONLY) RESTRICTED 3 10 A: D Adding weights lower the CG [E] such that the CG is below the pivot for stability. [C] [1] 11 A: D For hydraulic press system, pressure is transmitted from piston X to piston Y. 𝑃𝑥 = 𝑃𝑌; 𝐹𝑥 𝐴𝑥 = 𝐹𝑌 𝐴𝑌 ; 𝐹𝑌=𝐹𝑥 𝐴𝑦 𝐴𝑥 [C] E: reducing diameter of X and increasing the diameter of Y will increase the force to life the load at Y. [1] 12 A: B As the box moves up the rough slope, there would be some energy is transferred in the form of heat to the surrounding. [E] C: Principle of conservation of energy. [1] 13 A: B During boiling, the temperature of the liquid remains constant. [C] Thus the average speed of the particles remain constant and the internal kinetic energy of the particles will also remain constant. [E]. The energy taken in will be used to overcome the intermolecular forces of attraction between the particles. [A] Internal potential energy will increase. [1] 14 A: A Heat conduction [C] rate: [E] aluminium L 12 s to rise by 2C ✓ Copper L 6 s to rise by 2C Fibreglass L 77 s to rise by 2C ✓ Polystyrene L 30 s to rise by 2C 15 A: C E = mcT [C] c = 𝐸 𝑚∆𝑇 [E] 16 A: C C: Electrical energy supplied = Heat gain during boiling E: Pt = mLv 1500 x (700 -100) = 0.550 x Lv  Lv = 1600 kJ/kg 17 A: D • Frequency of the waves remain the same as it is dependent on the dipper (source). [C] • Speed of waves, v = f [C] = 2.5 x (3.0 cm) [E] = 7.5 cm/s [A] • This wave is ta transverse wave [C] • Wavefronts [C] are farther apart in the deep region and closer together in the shallow region as observed from the wavelengths.

CHR SEC 4 EXP SCIENCE PHYSICS (5086) PRELIM 2024 PROPOSED MARKING SCHEME (FOR TEACHERS ONLY) RESTRICTED 4 18 A: C Wavelength = 2.0 m (from displacement-distance graph) [E] Amplitude = 0.50 m (from both graphs) [C] Frequency = 1/T [C] = 1/ 4.0 = 0.25 Hz (from displacement-time graph) Speed = f [C] = (0.25 x 2.0) = 0.50 m/s [1] 19 A: D High frequency electromagnetic waves such as X-rays and -rays can cause ionising effects on living cells. [E] (not heating effects). Infra-red and especially ultraviolet rays result in heating effect ; skin cancer. Over-exposure to radio waves does not cause skin cancer. [1] 20 A: B Only student X can see the images of the other two students as shown. Student Y can only see image of student X but not student Z. Student Z can only see image of student X but not student Y. Object distance is same as image distance for plane mirror. [C] [1] 21 A: B Image is real, inverted and magnified. Magnification is 2.0 When object is placed less than focal length, image is upright and magnified. [C] When object is placed at twice focal length, image is same size. [C] [1] 22 A: A Electrical field pattern between a positive and a negative point charges. [C] [1] 23 A: D A, B and C are examples of potential hazard in electrostatic charging. D is a useful application of electrostatic. [E] [1] 24 A: C Q = It [C] 35 = I x 1.0 x 10-3 [E]  I = 35 000 A or 35 kA [A] [1] 25 A: B; Concept R = L/A R L D 4R L D/2 2R L/2 D/2 R/4 L 2D [1]

CHR SEC 4 EXP SCIENCE PHYSICS (5086) PRELIM 2024 PROPOSED MARKING SCHEME (FOR TEACHERS ONLY) RESTRICTED 5 26 A: C C: Effective resistance in series, parallel and combinations E: Effective resistance P Q R S 150  300  33  67   RSPQ from smallest to highest [A] [1] 27 A: D C: action of a variable potential divider (potentiometer) E: A short circuit occurs at 500  resistor. Therefore p.d. across 5.0 k is 5.00 V [1] 28 A: B C: the effect of temperature increase on the resistance of a metallic conductor and filament lamp E: As temperature increases, there is increase in vibration of the metallic atoms in their fixed positions. This increases the number of collisions between the free electrons and the metallic atoms, which in turn opposes or slows down the flow of free electron s. Therefore resistance increases and current flow decreases over time. [1] 29 A: B E: ✓ The annual unit cost of electricity = $542/1650 = $0.328 ✓ Total energy consumption per year = 1650 000 x 60 s x 60 min = 5.94 GJ ✓ When operating for 4.0 min, energy consumed E = VIt [C] = 2800 x 4.0 x 60s = 672 kJ  Operating current I = P/V [C] = 2800 / 230 = 12. 2 A [1] 30 A: D C: meaning of the terms live (brown), neutral (blue) and earth (green/yellow) [E] [1] 31 A: B C: P = IV [C] 40 = I (9.0) [E] I = 4.44 A [1] 32 A: B C: Soft iron is used for the core of electromagnet and copper wire is used for electromagnet. [E] [1] 8.88 A 4.44 A 4.44 A 4.44 A

CHR SEC 4 EXP SCIENCE PHYSICS (5086) PRELIM 2024 PROPOSED MARKING SCHEME (FOR TEACHERS ONLY) RESTRICTED 6 33