MFSS Prelim P1 Ans

- Page 1 - 2024 O-Level Prelim Physics 6091/01 Solution [40m] 1 D 2 B 3 D 4 B 5 B 6 B 7 A 8 C 9 C 10 C 11 C 12 C 13 B 14 B 15 D 16 A 17 B 18 D 19 D 20 C 21 B 22 C 23 B 24 D 25 B 26 A 27 A 28 D 29 D 30 D 31 A 32 B 33 B 34 C 35 C 36 B 37 D 38 B 39 B 40 C 5 B 11 C Taking pivot at F, 50 W = 75 P P = 50/75 W = 2/3 W 12 C Volume of shaded = 1 cm3 Mass of shaded = 6 g Volume of unshaded = 2 cm3 Mass of unshaded = 18 g Total mass/total volume = 24/3 14 B Change of volume is constant 6x = 1 (0.8) 20 C 22 C 23 B Refraction takes place. Nwater > Nair

- Page 2 - Vwater<Vair Frequency no change. 24 D v = 2d/t 1500 = 12000/t t = 8.00 s (time for pulse emit and receive) 8 + 2 = 10.0 s 26 A v=fλ f low, then λ is high 32 B W = QV = 90 x 3 x 1010 12024 O-Level Prelim Physics 6091/02 Solution [80m] Section A: Answer All Questions (50 + 10 (LQ) + 10 (Data) Marks) 1 ai a=∆୴∆୲ or a ୴ି୳୲ (2 points to be as wide as possible) or (58 – 50) / 0.20 (if lenient) any value from 35.0 to 43.0 m/s2 (3sf + SI unit) 𝐚 =𝐯𝐭 𝒎𝒆𝒂𝒏𝒔 𝟏 𝒑𝒐𝒊𝒏𝒕 𝒅𝒊𝒗𝒊𝒅𝒆𝒅 𝒃𝒚 𝟏 𝒑𝒐𝒊𝒏𝒕. 𝑰𝒕 𝒊𝒔 𝒂 𝒘𝒓𝒐𝒏𝒈 𝒇𝒐𝒓𝒎𝒖𝒍𝒂 𝒕𝒐 𝒖𝒔𝒆. 1 1 aii Taking upward resultant force as positive, FR = FA – W 1m for FR = ma ma = FA – mg FA = ma + mg = 76 x 40 + 76 x 10 and (students to transfer a from 1ai correctly) = 3800 N 1 1 1 b (deceleration because) upward force greater than weight or upward resultant force air resistance decreases (with decreasing speed / with time) or deceleration decreases or resultant (upward) force decreases B (until / finally) weight equals air resistance or forces balance or at terminal / constant velocity / speed 1 1 1 W FA

- Page 3 - 2 ai Since gravitational field strength decreases as object moves further from the planet, OR and because gravitational field strength is the greatest when Pluto is at X and AND therefore, speed decreases from X to Y. As gravitational field strength increases as Pluto moves from Y to X, therefore speed increases from Y to X 1 1 aii Since energy cannot be created or destroyed or energy can be transferred to one energy store to another, and because some energy in the gravitational potential store is transferred to kinetic store as Pluto moves from Y to X, therefore speed increases when Pluto moves from Y to X. 1 1 b (white surface) is a poor absorber / good reflector / poor emitter of IR / radiation OR black / other surface is a good absorber / poor reflector / good emitter of IR / radiation any one from:  (the white surface) increases in temperature less when facing the Sun  (the white surface) decreases in temperature less when facing away (from Sun)  the black / other surfaces increases in temperature more when facing the Sun  the black / other surface decreases in temperature more when facing away 1 1 3 a Since pressure is force per unit area, and because, the person is spread over a greater contact area therefore, the pressure is lower or ice is less likely to crack 1 1 1 b P (due to water) = gh OR = 1000  10  0.45 = 4500 Pa P =୊ ୅=୫୥ ୅ OR =଺ଽ଴ ୶ ଵ଴ ହ =1380 Pa P (due to X) = 4500 + 1380 = 5880 Pa 1 1 1 ai E = mc ∆  = 0.6 x 4200 x (21.5 – 19) = 6300 J 1 1 aii E = Pt = 13 x 500 = 6500 J Efficiency (light) = Useful energy output total energy inputx 100% =6500−6300 6500 x 100% 1 1

- Page 4 - = 3.08 % (3sf) or 3.1 % (2 sf) 1 b any one from:  temperature change is an underestimate due to thermal energy transferring out of the system  thermal energy is transferred from the water to internal store of the surrounding  energy (other than light) transferred in lamp (filament / glass / internal structure)  (some) water evaporates 1 5 a Since the angle of incidence is greater than the critical angle, and because, the light from the optically denser medium to optically less dense medium / glass windscreen to air therefore, the infrared light undergoes total internal reflection 1 1 bi The glass windscreen is the optically denser medium as it bends away from the normal as the infrared light leaves. 1 bii n=sin r / sin i = sin 62/ sin 47 = 1.21 1 1 c As the detectors received less percentage of infrared light reflected, means that there are more raindrops on the windscreen. The speed of the windscreen wipers will increase. 1 6 a Electric field is a region in which an electric charge experiences an electrostatic/electric force. 1 b (i) the beam of uncharged particles deflects upwards and is attracted to the positively charged plate. (ii) the beam of electromagnetic wave continues undeflected in a straight line. 2 c Since the gamma wave do not have a charge / no affected by electrical field, and because it does not attract to the plate, therefore it continues moving along a straight line. Since the negative charges will be induced to the (upper) side closer to the positively charged place, and because opposite charges attract, therefore the particles are attracted/move towards to the plate. 1 1

- Page 5 - 7 ai all circuit symbols correct for resistor, thermistor, a filament lamp and a power supply four components joined in series 1 1 aii voltmeter connected in parallel to the resistor 1 aiii current through resistor when p.d. across it is 6.0 V = 0.4 A Since this is a series circuit, 0.4 A flows through thermistor and bulb p.d. across filament lamp = 3.0 V AND p.d. across thermistor = 9.0 V p.d. across terminals of power supply = 6 + 3 + 9 = 18.0 V (3sf) or 18 V (2sf) 1 1 1 b any sensible use requiring temperature control or depending on temperature, e.g. fire alarms, to keep computers cool (by operating fan), in incubators, electronic thermometer, electronic thermostat in kettle / car engine 1 8 a 12 V 1 b R 40cm = 10 x 0.4 = 4 Ω Reff = 6 + 4 + 5 = 15 Ω I = V / R = 12/15 = 0.80 A p.d across resistance wire = IR = 0.8 x 4 = 3.20 V (no deduction for no formula) 1 1 1 c Since effective resistance decreases (due to 3 Ω and 6 Ω arranged in parallel), and because current flowing through battery increases therefore ammeter reading increases. And because current flowing through XJ increase and V = IR Therefore voltmeter reading increases OR And because using potential divider formula, when combined resistance of 3 Ω and 6 Ω is less than resistance of XJ Therefore voltmeter reading increases 1m for ammeter and voltmeter reading increases 1m for ammeter explanation 1m for voltmeter explanation 1 1 1

- Page 6 - 9 a yes no it is not possible to tell an alpha-particle 𝐻𝑒ଶସ is emitted ✔ a beta-particle 𝑒ିଵ଴ is emitted ✔ a gamma ray 𝛾଴଴ is emitted ✔ 2 for 3 correct OR 1 for 1 correct 1 1 (gamma) bi (count that is) always present or due to the environment / surroundings or not deliberately introduced or not being tested any one from: rock sources (e.g. benches, building materials, human body, Earth crust) air sources (e.g. radon) cosmic sources (e.g. Sun, space) 1 1 bii use tongs / tweezers / forceps or wear lead(-lined) clothing / lead(-lined) gloves or wear goggles or reduce time of exposure or keep distance of separation large 1 biii (radioactive) emission is a random process / occurs at random intervals measurements fluctuate (about an average value) 1 biv (coordinates of) two points from curve, e.g. (0, 58) and (70, 29) (coordinates of) two points from curve and at least two half-lives apart, e.g. (0, 58) and (138, 14.5) or 64.0 ⩽  ⩽ 74.0 66.0 s ⩽  ⩽ 73.5 s 1 1 bv (large half-life because of) slow rate of decay radiation / count rate due to Uଽଶଶଷସ (uranium) is imperceptible / very much less than that o