Xinmin_4N_Prelims_2022_Physics_Marking_Scheme

4NA Prelim Science (Physics) Paper 2022 Paper 1 (20 marks) 1 2 3 4 5 6 7 8 9 10 A C A B C A D A D B 11 12 13 14 15 16 17 18 19 20 D C D B C B A A A A Paper 2 Section A (14 marks) 1a Nm or Ncm [1] 1b A because it is further away from the hinge of the door. [1] Total [2] 2a Using a rubber creates a better grip due to friction. [1] 2b Pour hot water over the cap only. The hot water will expand the cap as matter expands when heated. [1] [1] Total [3] 3a i. 3a ii. The speed of the car increases. The speed of the car is a constant. [1] [1] 3b average speed = 60 000 / (40 x 60) = 25 m/s [1] [1] Total [4] 4a The water at the bottom near the heater is heated and expands. It becomes less dense and rises. The relatively denser cooler water at the top will sink. Convection currents are set up. [1] [1] 4b Air is a poor conductor of heat. Lagging minimize heat lost by the hot water to the surrounding. [1] 4c Shiny surfaces are poor emitters of radiation/poor radiators of heat. [1] 4d Water is heated up faster. [1] Total [5]

Paper 2 Section B (16 marks) 5a Vibration from the source displaced the air particles next to it. The air particles will move closer and further apart from each other continuously. / A series of alternate compressions and rarefactions travel through the air from the source. [1] [1] 5b i 5b ii 5b iii The number of complete waves produced in one second. wavelength = 320 / 1000 =0.32 m distance btw Pt A and D = 0.32 (3) = 0.96 m = 96 cm 5.0 ms = 0.005 s frequency = 1/0.005 = 200 Hz [1] [1] [1] [1] [1] [1] [8] 6a Energy can neither be created nor destroyed in any process. It can be converted from one form to another but the total amount remains constant. [1m for any 2 points stated] [2] 6b h = 6 cm = 0.06 m GPE = 0.008 (10) (0.06) = 0.0048 J [1] [1] 6c 0.0048 J [1] 6d 0.5 (0.008) v2 = 0.0048 v2 = 1.2 v = 1.1 m/s [1] [1] 6e There are resistive forces such as friction on the track and air resistance [1] [8] 7a A: ammeter B: voltmeter [1] [1] 7b axis correctly labelled with correct intervals all 5 points plotted clearly with crosses straight line drawn through the crosses neatly [1] [1] [1] 7c all 5 points plotted clearly with crosses straight line drawn through the crosses neatly [1] 7d Resistor Y has a lower resistance than resistor X. The gradient for resistor Y is smaller than resistor X. / For each value of current, [1] [1]

voltage for resistor Y is smaller. (V=RI) Total [8]