DHS 2020 JC1 Promos Physics (Solutions)

DUNMAN HIGH SCHOOL 2020 PHYSICS H2 (YEAR 5) 1 Answers to Promo Exam MCQ Q1 Q2 Q3 Q4 Q5 Q6 Q7 Q8 Q9 Q10 D B D D C D D C B A Q11 Q12 Q13 Q14 Q15 D A B B B Structured Questions 1(a) 2 of the following: -temperature, kelvin -current, ampere -amount of substance, mole -luminous intensity, candela 1 mark for each correct quantity and unit, correctly spelled (no caps). [2] MC: It is surprising that more than half the cohort cannot remember the SI base quantities and units. Some students didn’t write in words, instead using only symbols hence no credit. Lastly, for units, the spelling should be all small letters, i.e. kelvin instead of Kelvin. This point wasn’t penalized for this exam, but please remember next time. (b) units of E: kg m2 s-2 , units of ρ: kg m-3 , units of g: m s-2, units of A: m2, units of L: m C1 units of C: kg m2 s-2 / kg2 m-6 m2 s-4 m2 m3 C1 = kg-1 m s2 A1 [3] MC: Some students left answers in J or N, which are not base units. (c) radius = (10.0 ± 0.1) mm Volume V = π r2 h = π (10)2 (1.5) = 471.2 mm3 --- (M1) ΔV / V = 2Δr / r + Δh / h ΔV = (2Δr / r + Δh / h) V = [2(0.1/10) + (0.1/1.5)](471.2) = (0.02 + 0.067) (471.2) = 40 mm3 (1 s.f) --- (M1) Therefore V = (470 ± 40) mm3 --- (A1) [3] MC: Many students left answer as (471 ± 40) mm3. This is a misconception. Note that the uncertainty is in the “tens” decimal position, hence the quantity should be also rounded to the same decimal position i.e. “tens” position.

DUNMAN HIGH SCHOOL 2020 PHYSICS H2 (YEAR 5) 2 2 (a) Use of mgh = ½ m v2 C1 h = 14.7 or 15 m A1 (b) (i) vY = uy + ayt = 0 + (9.81) (1.6) C1 = 15.7 or 16 m s-1 A1 (ii) Straight line of positive gradient B1 S tarting at 0 m s-1 and ends at 16 m s-1 at 1.6 s. B1 ( iii) resultant v2 = 15.72 + 172 C1 v = 23 or 23.1 m s-1 A1 MC : Majority of candidates did well in this question. A few used the slope angle to calculate the vertical component of velocity at C which was incorrect. Q3 MC For similar questions, refer to - 2019 DHS Promo Structured Question 2 - 2020 DHS Dynamics Lecture Example 13 - 2015 A-level H1 Q7 - 3(a) 0.76 + 0.48 = 1.24 m s-1 A1 (b) 1.24 m s-1 A1 MC For e.c.f, ans should be identical to (a)

DUNMAN HIGH SCHOOL 2020 PHYSICS H2 (YEAR 5) 3 (c) Before collision, After collision, By conservation of linear momentum, 5.2(0.48) 2.3(0.76) 5.2 2.3 0.748XYVV− =+= ---