Northland 4N SCI PHY PRELIMS 2022 - ANSWERS

Northland Secondary School Secondary 4 Normal Academic Science Physics Preliminary Examination 2022 Marking Scheme Paper 1 1 2 3 4 5 6 7 8 9 10 D C B D C A B A C C 11 12 13 14 15 16 17 18 19 20 B B B A A A C B B C Paper 2 [Section A] 1 (a) Gravitational potential energy = mgh = 7 x 10 x 10 = 700 J [1 mark for answer] 1 (b) By COE, loss in GPE = gain in KE Gain in KE = 700 J 700 J = 1 2 𝑚𝑣2 700 J = 1 2 (7)𝑣2 [1 mark for correct application of equation] 𝑣2 = 200 v = 14.1 m/s (3s.f) [1 mark for answer] 1 1 (c) The speed of the object would still be the same as the answer in (b), since the loss in GPE is still at 700 J as the height remains at 10 m. Note: Student has to give the correct explanation in order for the mark to be awarded; as long as student is able to state that the height remains the same. 1 2 (a) 100 m represents 3 wavelengths. Thus, 1 wavelength = 100 ÷ 3 = 33.3 m [1 mark for answer] 1 (b) It takes 49 seconds to complete 7 waves (from A to B). Thus, the period of a single wave = 49 ÷ 7 = 7 s [1 mark for answer] 1 (c) 𝑣 = 𝜆 𝑇 = 33.3 7 [1 mark for correct application of equation] = 4.76 m/s (3s.f) [1 mark for answer] 1 1 Setter Mr Lim Yong Liang Vetter Mr Aaron Rajoo

3 Note: For full credit, student needs to get all 3 blanks correct. 1 mark would be awarded for students who get 1 or 2 blanks correct. arrangement movement solid packed closely in an orderly arrangement vibrates about in its fixed positions liquid packed closely in a disorderly arrangement slides over/across one another gas packed far apart in a random arrangement moves rapidly and randomly in all directions 2 4 (a) All points are located correctly. All crosses are drawn appropriately. 1 1 (b) Curve is drawn correctly and passes through all points. 1 (c) 82 C 1

Paper 2 [Section B] 5 (a) Work is done on the barbell as the barbell moves in the direction of the force applied by the F1 driver. Note: Student has to give the correct explanation (sound and logical) in order for the mark to be awarded. 1 (b) W = mg = (50 + 75) x 10 = 1250 N [1 mark for answer] 1 (c) 𝑃 = 𝐹 𝐴 = 1250 2 ×0.2 [1 mark for correct application of equation] = 3125 N/m2 [1 mark for answer] 1 1 (d) Design A is preferred, as Design A adopts a broader base. [1 mark for correct choice and reasoning] This makes the car more stable. [1 mark for correct conclusion] 1 1 (e) (i) average speed = total distance total time = 5063 105 = 48.2 m/s (3s.f) [1 mark for answer] 1 (ii) average acceleration = 𝑣−𝑢 t = 75−0 10 = 7.5 m/s2 [1 mark for answer] 1 6 (a) material chosen: dull white canvas sheet reason 1: white is a poor absorber of heat, thus it is less likely to cause the makeshift shelter from being too warm. reason 2: canvas sheet is a poor conductor of