Pure Physics Nov 2017 TYS ANSWERS

Nov 2017_Suggested ANSWERS_as at June 2023 Page 1 of 6 – Nov 2017 Catholic High School | O-Level Physics NOT IN SYLLABUS: 5059 Nov 2017 P1: - Suggested Answers P2: - Paper 1 [40 marks] 1 D 11 C 21 A 31 D 2 B 12 B 22 D 32 B 3 D 13 B 23 B 33 D 4 B 14 A 24 A 34 B 5 B 15 A 25 D 35 C 6 C 16 C 26 D 36 A 7 B 17 D 27 A 37 A 8 C 18 A 28 B 38 B 9 B 19 C 29 A 39 D 10 D 20 C 30 C 40 C *Q. 15: A The force per collision is greater (due to the gas molecules having greater speed). Since pressure of the gas remains the same, then the rate of collisions must have decreased. If the rate of collisions increased or stayed constant, the pressure would have increased given that the force per collision is greater. (Both B and C are incorrect.) *Q. 25: D Statement 1 was incorrect. The speed of light is 3.0 × 108 m/s only in vacuum. (B is incorrect.) *Q. 35: C If the question does not indicate otherwise , assume the resistance of a thermistor will increase with a decrease in temperature (i.e. when it is cold). The LDR would have low resistance when the surroundings are bright. (D is incorrect.) *Q. 40: C A decrease in the resistance of the cables as the cause of the more efficient transmission of electrical energy at high -voltage is a common misunderstanding. (B is incorrect.)

Nov 2017_Suggested ANSWERS_as at June 2023 Page 2 of 6 – Nov 2017 Paper 2 [80 marks] 1 a prefix symbol value milli m 10-3 mega M 106 kilo k 103 nano n 10-9 3 b acceleration density speed time volume weight 1 c Length of R = 5.4 cm Magnitude of R = 5.4 × 2.0 = 10.8 m/s (3 s.f.) 1 1 1 2 ai When an object is in equilibrium, the sum of clockwise moments about any point is equal to sum of anti- clockwise moments about the same point. 1 1 aii Taking moments about the wheels, Sum of clockwise moments = Sum of anticlockwise moments F1 × d1 = F2 × d2 12 × (21 + 4.0) = W × 4.0 W = 75.0 N (3 s.f.) 1 1 b With the heavier contents near the base, the centre of gravity of the suitcase is lower. The line of action of the weight is more likely to fall within the base area when the suitcase is tilted. 1 1 c The normal reaction (or contact) force acting on the suitcase by the ground. This force acts upwards (on the wheels of the suitcase), and is equal to the normal reaction (or contact) force acting on the ground by the suitcase. 1 1 3 ai The gas supply exerts a pressure on the water surface on the left that is greater than atmospheric pressure on the right.] 1 aii The gas pressure on the left is equal to the total pressure due to 9 cm of water column and atmospheric pressure. 1 b Pressure difference = hρg = [(17 - 8 )/100] × 1000 × 10 = 900 Pa (3 s.f.) 1 1 c Use a liquid of higher density (e.g. mercury). 1 horizontal velocity vertical velocity R

Nov 2017_Suggested ANSWERS_as at June 2023 Page 3 of 6 – Nov 2017 4 a Work done by a force is the product of the force and the distance moved in the direction of the force. 1 b Work done = Gain in GPE = mgΔh = 3.9 × 10 × (0.95 × 2) = 74.1 J (3 s.f.) 1 1 c Power = Work Done Time = 74.1 30 × 60 = 0.0412 W (3 s.f.) [Note: Time taken for the minute hand to move from pointing vertically downwards to upwards is 30 minutes.] 1 1 5 a Amplitude = 1.50 cm (2 d.p.) [Note: Each wide division is read to a precision of ½ division of 0.25 cm.] 1 bi Frequency is the number of complete oscillations per unit time. 1 bii Period of the wave = 0.8 s (1 d.p.) [Note: Each wide division is read to a precision of ½ division of 0.1 s.] Frequency, 𝑓 = 1 𝑇 = 1 0.8 = 1.25 Hz (3 s.f.) 1 ci * Shortest distance between points A and B = ¼λ v = f λ = (1.25)(4 × 38) = (1.25)(152) = 190  200 cm/s (shown) [Note: When point A is at the crest, point B is at the equilibrium position. Hence shortest distance between points A and B = ¼λ.] 1 1 cii * The possible distance between points A and B can be (n+ ¼)λ, where n is an integer. Hence, there are many possible values for λ. [Note: ‘Loss of energy to the surroundings air’ is not accepted as the amplitude of the graphs is constant.] 1 6 a • Switch on the live wire • Circuit breaker • Earth wire connected to the metal casing • Double insulation of cables 2 Any two bi Current , 𝐼 = 𝑃 𝑉 = 800 230 = 3.48 A (3 s.f.) 1 1 bii The 5 A fuse should be used. The 3 A fuse will melt each time the toaster is switched on. The 13 A fuse may not melt when a high current flows (e.g. due to an electrical fault), and can cause overheating of the cables. 1 1 7 ai 1 aii By using Fleming’s Left Hand Rule. The thumb will point in the direction of the forces on AB (donwards) and CD (upwards), when the first/index finger points in the direction of the magnetic field (left to right) and the middle finger points in the direction of the current (A to B and C to D respectively), and all three directions are perpendicular to each other. 1 1

Nov 2017_Suggested ANSWERS_as at June 2023 Page 4 of 6 – Nov 2017 [Note: A simple diagram to illustrate this can be drawn by the side.] b When AB reaches the lowest point (the coil is in the vertical position), the current in the coil is reversed. This ensures that the force acting on AB near the same magnet is always in the same direction (e.g. the force acting on AB near the north pole is always downwards). 1 1 8 a Iron is a magnetic material. The left side of the iron ring becomes an induced south pole and is attracted to the north pole of the bar magnet as unlike poles attract. 1 1 b Aluminium is a non-magnetic material. 1 ci When the magnet moves close to the aluminium ring, the ring experiences a change in magnetic flux linkage with the magnet. By Faraday’s Law of Electromagnetic Induction, there will be an induced emf and hence an induced current as the circuit is closed. 1 1 cii By Lenz’ Law, the induced current in the ring will flow in such a way that its magnetic effect will oppose the change causing it. As the N-pole of the magnet is being brought closer to the ring, the current in the ring will flow to set up a N -pole on the l eft side of the ring to repel the approaching magnet as like poles repel. 1 1 9 a Flint glass and cinnamon oil. [Note: They both have a refractive index of 1.601.] 1 bi c = 3.0 × 108 m/s 1 bii Crown glass. [Note: Crown glass has the highest refractive index. The larger the refractive index of a medium, the slower light travels in the medium.] 1 biii n = 𝑐 𝑣 v = 3.0 × 108 1.333 = 2.25 × 108 m/s (3 s.f.) 1 1 ci The angle of incidence of the light ray on the piece of glass is greater than the critical angle of the silicone oil. Hence, t otal internal reflection occurs in silicone oil which has a larger refractive index than the piece of glass. [Note: Need to use ideas about ‘angle of incidence, critical angle and refractive index.] 1 2 cii Car headlight glass (refractive index = 1.478). From Fig. 9.2, total internal reflection occurred, which means that the refractive index of the glass must be less than that of silicone oil (1.520). From Fig. 9.3, the light ray bends towards the normal when travelling from glycerol into the glass, which means the refractive index of the glass is greater than that of glycerol (1.466). 1 1 10 ai Between A and B: The velocity is increasing at a constant rate. (OR: The acceleration is constant.) 1 force magnetic field current

Nov 2017_Suggested ANSWERS_as at June 2023 Page 5 of 6 – Nov 2017 aii Between B and C: The velocity is increasing at a decreasing rate. (OR: The acceleration is decreasing.) 1 aiii Between E and F: The speed is increasing at a constant rate (OR: the velocity is decreasing at a constant rate OR: the acceleration is constant) AND it is moving in the backwards direction. (OR: The a