ANDSS 2025 Physics Prelim P2 MS

Answers to 2025 4E PHYSICS PRELIM PAPER 2 Sf and unit - unlimited Qn Answer Marks Comments 1 correct diagram magnitude between 40 to 48 kN angle between 18˚ to 26˚ [1] [1] [1] 2a At equilibrium, Clockwise moment = Anti-clockwise moment W x d1 = F x d2 F = (2.2 × 10 × 11)/24 = 10 N [1] [1] b - Since the centre of gravity is at the pivot, there is no perpendicular distance between the line of action of its weight to the pivot - no resultant moment / turning force acting on sculpture [1] [1] 3a(i) Pl = hρg = 1.0 x 1.6 x 104 x 10 = 1.6 x 105 Pa P = Pl + Patm = 1.6 x 105 + 1.0 x 105 = 2.6 x 105 Pa [1] [1] (ii) F = PA = 2.6 x 105 x 4.0 x 10-4 = 100 N (2s.f) [1] Full ecf b - the liquid in tube falls - liquid in tube stop falling and remains at a certain height - pressure of liquid inside the tube is equal to atmospheric pressure / pressure of liquid inside tube is originally higher than pressure of liquid in container immediately beneath glass sheet [1] [1] [1] 20 kN 50 kN FN 30º

4a Ep = mgh = 16 x 10 x 1.8 = 290 J (2sf) [1] b P = E / t = 288 / 4.5 = 64 W [1] c Total energy remains the same in the system Some energy from the chemical potential store of the motor is transferred by propagation of wave to the surroundings / to internal store of the conveyor belt [1] [1] 5a M - gamma ray Uses: Radiotherapy / sterilization of medical equipment / killing germs in food / detecting defects in manufacturing / treat cancer through Gamma knife radio surgery / kill cancer cells through directing gamma rays at tumours N - microwaves Uses: satellite communication / microwave oven / wi-fi signals / radar / mobile phone communication / cancer treatment / global positioning system [1] [1] b(i) Cell death or mutations leading to diseases or organ failure or cancerous growth [1] (ii) X-rays may interact with a particular atom or molecule and knocks an electron out from it, resulting in a charged ion / High frequency X-rays can penetrate deep into body to create ion The ion may hinder a certain chemical reaction which affects a particular cell process, affecting the specific biological system [1] 6a Critical angle of a diamond is the angle of the incidence in the diamond (optically denser medium) when the angle of refraction in the air (optically less dense medium) is 90⁰. [1] b(i) n = sin i / sin r = sin 35 / sin 15 = 2.2 (2sf) [1] [1] (ii) n = 1/ sin c 2.22 = 1/ sin c c = 27⁰ (2sf) [1] c(i) 75˚ [1] (ii) Angle of incidence is greater than critical angle and light is travelling from optically denser to less dense Total internal reflection is taking place [1] [1]

7a Reff = (1/1.5 +1/6.0)-1 = 1.2 Ω I = V / Reff = 12 / [1.3 + 1.2] = 4.8 A [1] [1] b As temperature increases, the resistance of the thermistor decreases. Effective resistance across 1.5 ohm resistor and Z decreases. The ratio of 1.3 ohm resistor to total resistance increases / since V = 1.3 𝑡𝑜𝑡𝑎𝑙 𝑟𝑒𝑠𝑖𝑠𝑡𝑎𝑛𝑐𝑒 × 𝜀 , causes the p.d. across to increase , hence causing the p.d. across the voltmeter to increase. [1] [1] c(i) The permanent magnet would induce the side of object A closer to the permanent magnet with a S-pole. Since unlike poles attract, object A would move towards the magnet and fall in container Y. [1] [1] (ii) Steel is a hard magnetic material and it loses magnetism slowly. [1] 8a - magnetic field of the coil interacts with the parallel magnetic field of the permanent magnet, - producing an upward force on the right side of the coil and a downward force on the left side of the coil. - By Fleming’s Left Hand Rule, magnetic field is directed to right and current in coil is away from A / towards B [1] [1] [1] b stronger magnetic field / soft magnetic material concentrate magnetic field lines, resulted in stronger force [1] c(i) P = IV 1200 = I (230) I = 5.2 A [1] [1] (ii) 8A fuse A fuse rating of 5A is lower than the working current and the fuse will melt. A fuse rating of 13A is much higher than the working current. When the current is too high but not melting the fuse yet, the motor may be overheated. [1] [1] 9a(i) Use gloves and tongs to pick up radioactive materials / wear protective clothing / accept other possible answers [1]

(ii) For controlling exposure to ionsing radiation / prevent leakage of radiation to surroundings / protect people from harmful effects of radiation [1] (iii) β−1 0 γ0 0 [1] [1] b(i) Nuclear radiation in the environment without a known radioactive source [1] (ii) Count rate from 58 → 29, Half-life = 66 s or Count rate from 29 → 15, Half-life = (134 – 66) s = 68 s Range = 60 - 72 s [1] [1] 10a(i) magnetic field lines of iron bar cuts the flat coil or magnetic flux / field change in the flat coil due to alternating current induces an e.m.f. [1] [1] (ii) larger rate of change of field / flux in the flat coil or larger rate of cutting of field lines in the flat coil [1] b(i) Soft magnetic material / easily magnetized and easily demagnetized / concentrate magnetic field lines within itself and improves links between primary and secondary coil. [1] (ii) Vs / Vp = Ns / Np Vs = (50 / 800) 240 = 15 V [1] [1] (iii) Efficiency = (Output power / input power) x 100 % = (3.2x15 / 0.22x240) x 100 % = 91 % [1] [1] (iv) By increasing voltage, the current can be lower Power loss in wires, P = I2R. Power loss will be reduced. [1] [1] 11a(i) Air trapped inside corrugated cardboard, is a poor conductor of energy / poor thermal conductor [1] (ii) Mug N has lower heat capacity, absorbed lesser energy per unit temperature rise Lesser energy from coffee will be transferred away by mug [1] [1]

b(i) Conduction and convection cannot occur Energy from gas will not be transferred through the glass wall to the surrounding. [1] [1] (ii) - average speed of particles decreases as average kinetic energy decreases - the particles collide with the walls of the container less frequently, exerting lesser force per unit area on the walls. [1] [1] c(i) Q = mcθ = 40 (0.39)(25+196) = 3400 J (2sf) [1] [1] (ii) Q = ml 3447.6 = m (200) m = 17 g (2sf) [1] 12a(i) Distance = area under the graph 830000 = ½ (11000) t t = 150 s [1] [1] (ii) a = 𝑣−𝑢 𝑡 = 11000−0 150 = 73 m/s2 [1] [1] Ecf (a)(iii) FN = ma = F – W F – (22000 x 10) = 22000 (73) F = 1 800 000 N [1] [1] (b) Rocket exhaust exert a force against the rocket, It is equal in magnitude and opposite in direction. [1] [1] (c) FN = T – W, FN increases since weight decreases FN = ma, mass decreases Acceleration increases [1] [1] 13a Layer of steel molecules are displaced Transmit through a series of compression and rarefaction Direction of vibration is parallel to the direction of travel [1] [1] b Maximum displacement of the pulse from rest position is reduced/smaller. [1] c(i) 15 µs since the distance travelled by the pulse is further before reflecting. [1]

(ii) v = 2d / t 5200 = 2d / (15x10-6) d = 0.0390 m [1] [1] (iii) Some of the sound waves are reflected away in other direction / absorbed by steel / not reflected back and instead transmit through the steel block. [1] (iv) - amplitude is between 25 – 40 µV - time is approximately between 5 – 15 µs [1] d density of solids is higher than that of liquids therefore particles of steel are closer together than seawater particles. molecules can pass on the energy from one molecule to the next faster [1]