Woodgrove 4NA Physics 5105 ANS KEY

WGS sec 4 NA Prelim 2022 Science Physics (5105) Answer Scheme Paper 1 Q1 B Q6 B Q11 C Q16 D Q2 C Q7 D Q12 A Q17 A Q3 C Q8 B Q13 A Q18 B Q4 A Q9 D Q14 A Q19 C Q5 D Q10 D Q15 B Q20 B Paper 2 Section A (16 marks) Note: Answers in fractions: - 1 m for whole paper NO half marks to be awarded Q Answers Marks Remarks 1 quantity unit mass kilogram resistance ohm weight newton electromotive force joule per column [2] [2] all 4 correct answers [1] any 2 correct answers [0] 1 or 0 correct answer 2 (a) [1] Acept either point of trough, labelled correctly and clearly with letter T. (b) Wavelength = =45 4 20 cm9 [1]

(c) Frequency of wave 1f = T 1f = = 0.10 s10 [1] (d) Speed of wave   v = f v = 0.1 20 = 2 m/s Unit : m / s (also accept metres per second) [1] [1] 3 (a) Method 1 – shift the small rock closer to the big rock. Method 2 – apply the force further away from the small rock, shift point A backward towards end of metal rod. [1] Accept either one of the two methods. (b) Method 1 and 2 – shift the small rock closer to the big rock OR apply the force further away from the small rock This will increase the moment or turning effect of the force, thus reducing the minimum force required. [1] Minimum force is reduced BECAUSE the moment of a force increases. 4 (a) [1] At least one arrow of conventional current must indicate clearly passing through from top to bottom of diagram. (b) Current through resistor VI = R 10I = 5 I = 2A [1] [1] Apply formula correctly I = V/R

(c) Effective resistance = 0.25Ω 1 1 1 R R R 1 1 1 45 11 20 20 effective resistor lamp R R R =+ =+ = = [1] [1] Apply effective resistance Section B Answer any two questions in the spaces provided. 5 (a) [1] [1] Correctly plotting of all points with a cross (x) Correct straight lines connected all the correct crosses. (b) (i) acceleration = (change in speed) / time 240 0= 2 m/s20 − = [1] (ii) The car is travelling at constant speed from time 20s to time 30s. [1] (iii) Total distance travelled = total area under speed - time graph ( )1= 10 40 402 1000m + = [1] [1] Award mark if student show correctly the method calculating total area. E.g. using trapezium or triangle, rectangle areas (c) (i) Possible answers • Road conditions (wet or dry, smooth or rough), [1] Any reasonable answer that will affect the braking

• tyres grip on the group, • Mass of the car time. Do not accept answer to increase the braking force, brake harder. (ii) • The time for the car to come to a stop after brakes is applied is dependable on the amount of friction force between the road and the tyres of the car. • Another possible answer is the mass of the car, if the mass of the car is increased/decreased, due to inertia force, the time needed for the car to stop will also change. [1] The explanation must be link to answer in (i). 6 (a) (i) Conduction - Heat is transferred from the hotplate to the metal pot and to the water through the vibration of particles (and free electron diffusion). Convection - As the water nearer to bottom gets heated up, its density decreases and it rises. The cooler water at the top then sink to the bottom as its denser. This creates a convection current that transferred heat energy from bottom to the [1] [1] Student explained the process of conduction through vibration of particles Student describe the movement of fluid in convection process. (ii) Radiation / infrared radiation / thermal radiation [1] (iii) Metal contains free electrons that enable higher rate of heat conduction. [1] (b) (i) P =I V PI = V 1560I = 6.5A240 = [1] (ii) 8A fuse, the selected fuse rating should be slightly higher than the normal operation current. [1] Accept ecf based on answer in part (i) (iii) Total power used

EP = t 40E = 1.56kW 1.04kWh60= Cost of electricity 1.04kWh 0.25 =$0.26  [1] [1] [1] 1.04 kWh 7 (a) (i) Stability refers to the ability of an object to return to its original position after it has been tilted or displaced slightly [1] (ii) Neutral equilibrium [1] 7 (b) (i) gravitational potential energy GPE = mgh GPE = 0.6 10 10 GPE = 60J  [1] [1] Apply GPE = mgh (ii) KE = 60 J [1] Accept ecf, from part (i) (ii) 2 2 1KE = mv2 160 = (0.6)v2 v =14.14 v =14.1 m/s [1] [1] Accept ecf, from part (i) Apply correctly KE formula (iv) Energy is lost to the surrounding after the first bounce. (air resistance, sound and heat energy lost during energy conversion) [1]