2023 AHS Prelim Exam P2 mark scheme with marker's comments

2023 S4 Physics Prelim Exam Paper 2 mark scheme & markers’ comments 1(a) w to x: displacement decreases at an increasing rate / decreases non-uniformly in the negative / downwards direction. x to y: displacement increases at an increasing rate / increases non-uniformly in the negative / downwards direction. All 4 points - 2 marks, 2-3 points - 1 mark, otherwise - 0 (b) 1 (c) 3

Marker’s comments a) Students need to know displacement is positive or negative based on position, but velocity is positive or negative based on direction. When the question asks for direction of motion of object, it is moving downwards or towards the negative direction. Many candidates did not answer the question - addressing the change in displacement and the rate but they wrote about velocity and acceleration. They need to know that we can’t tell the rate of change of velocity from the graph given. b) Height is a distance. In order to know the height, marking out displacement at zero will not help even though that corresponds to the top of his head. c) Many candidate did not label the area under the graph and some label wrongly. This area must be formed with the time axis. NOTE that if you are using the second answer, all 5 correct, 2 marks, 2(a) 80 J (minus 1 mark for wrong or no unit) 1 (bi) Weight 1 (bii) Any diagonal straight line with a less steep gradient. 1 (c) EK gained = EP lost or ½ m v2 = m g h or v = √(2gh) or v = 2 x 10 x 3.25 v = 8.06 m/s (3 s.f.) or 8.1 m/s (2 s.f.) minus 1 mark for no or wrong unit 1 1 Marker’s comments a) Common mistake is reading values off wrongly due to incorrect scale. Many were not aware that there are only 4 small divisions between 1.0 m. bi) Many students chose mass as their answer, which is incorrect. Some students are still unsure of the difference between mass and weight. ‘Force’ was accepted even though the gradient gives a specific quantity (from mgh/h = mg), which is weight.

ii) Very well done. c) Common mistake is to equate ½ v2 = 80, where 80 is the value of EP. Some used the gradient, which they thought was mass, in their calculations. Method mark was awarded. 3(a) It is the point through which its whole weight appears to act. 1 3(b) 2 (c) Upwards force / Tension / Spring force increases. Since the mass is in equilibrium (or Net force is zero) with an additional downwards force applied, the upwards force/tension must have increased. 1 1 (d) Upwards tension is more than downwards weight, Or As there is a net upwards force, from F = ma mass will accelerate upwards. 1 1 1 Marker’s comments a) Many cited ‘on the object’ and were penalised, as the c.g. may not be on the object. Many students clearly has not put in the effort to memorise their definitions, which is