Pure Physics DBQ Package (answers)

CHS Data-based Questions Skills Package – Suggested Answers 1 1. CGS: Mechanics (+ Thermal Physics) [GRILS/Practical Planning] Qn Part Suggested Answers Marks Remarks 9 (a) 𝑄 = 𝑚𝑐𝛥𝜃 Q = 0.0010 × 4200 × 1.0 = 4.2 J A1 (b) Work done against weight = GPE gained = mgh = 50 × 10 × 201 = 100500 J = 1.0 × 105 J (2 s.f.) M1 A1 Accept answer to 2 or 3 s.f. (c) Min amount of energy from carbohydrates = 60% × 100500 = 60300 J Min amount of calories provided = 60300 / 4.2 = 14357 Min mass of carbohydrates needed = 14357 / 4000 = 3.59 g M1 A1 Allow ECF from (b) (d) Use calibrated electronic balance to measure his mass m. Use metre rule to measure the height of one step, h, of the staircase. Count the total number of steps, n, that he has to run up. The total height that he runs up to will be H = nh. Using a stopwatch, record the time taken t for him to reach H. His average power can then be calculated from Pave = mgH / t. Repeat the above steps at least 2 more times. Take the mean of Pave for a more accurate answer. B1 B1 B1 B1 1 m for stating the 3 main measuring instruments and their corresponding physical quantities 1 m for stating the formula for average power Pave 1 m for describing a clear and sensible procedure 1 m for repeating and taking the mean of Pave (e) t = E / P = 100500 / 48 = 2.1 × 103 s A1 Allow ECF from (b)

CHS Data-based Questions Skills Package – Suggested Answers 2 2. HCI: Mechanics [GRILS] Qn Part Suggested Answers Marks Remarks 9 (a) 𝐾𝐸 = 1 2 𝑚𝑣2 = 0.5 (0.025) (56)2 = 39.2 = 39 J M1 A1 (b)(i) v = u + at 0 = 56 + a(0.020) a = −2800 m/s2 deceleration = 2800 m/s2 M1 A1 (ii) 𝐹𝑛𝑒𝑡 = 𝑚𝑎 f = (0.025)(2800) f = 70 N M1 A1 (c) Work done = fd = (70)(0.12) = 8.4 J M1 A1 (d) Loss in KE = WD against friction + Gain in GPE 39.2 = 8.4 + mgh 39.2 = 8.4 + (0.025 + 8.0) (10) h h = 0.3838 = 0.38 m (theoretical value) However, experimental value = 0.292 m, hence there is a discrepancy M1 Aa1

CHS Data-based Questions Skills Package – Suggested Answers 3 3. Nan Chiau: Mechanics (+ Thermal Physics + Magnetism and Electricity) [GRILS/PRC] Qn Part Suggested Answers Marks Remarks 10 (a) 80 − 50 = 30 m A1 (b) Any possible reason: -To protect the wind turbine from damage due to its blades being ripped off / wear and tear / prevent turbulence or prevent the generator being burnt out or catastrophic failure -Stop working during hurricane -Current too high causing fuse to melt and open circuit so not wo