2025 RVHS H2 Physics P2 Soln Prelim

River Valley High School Page 1 of 10 J2 H2 Physics 9749 2025 JC2 Preliminary Examinations 2025 RVHS JC2 H2 Physics Preliminary Examinations Paper 2 Mark Scheme Questions Answers Marks 1 (a) (i) The gas molecules move randomly (and rapidly) B1 (ii) The volume of their molecules is negligible compared to the volume of the containing vessel. B1 (b) (i) The gas molecules move in three dimensions (or x- , y- and z- direction.) B1 (ii) Using 𝑝 = 1 3 𝜌 < 𝑐2 >, we get 101 000 = 1 3 × 1.25 × √𝑣 M1 𝑣 = 492 m s−1 A1 (iii) Kinetic energy of ideal gas ∝ 𝑇, and Kinetic energy of ideal gas ∝ 𝑣𝑟𝑚𝑠2 so 𝑣𝑟𝑚𝑠2 ∝ 𝑇 M1 𝑣 492.34 = √273.15 + 127 273.15 𝑣 = 596 m s−1 award M1 mark if temperature not given in thermodynamic temperature, but A0 A1 Questions Answers Marks 2 (a) Its acceleration is directly proportional to its displacement from a fixed point (equilibrium position) and is always directed towards that fixed point. B1 (b) gain in gPE = mgh C1 (0.150)(9.81)(1.0 × 10−3) = 1.4715 × 10−3 ~ 1.5 × 10−3 J A1

River Valley High School Page 2 of 10 J2 H2 Physics 9749 2025 JC2 Preliminary Examinations (c) (i) (ii) B1 B2 (d) From calculation in (b), total energy is 1.5 × 10−3 J So the horizontal displacement should be 40 mm B1 (e) Direction of displacement must be opposite to that of velocity, i.e. if line is in positive displacement, velocity must be in negative region Subsequent quarter of oscillation must decrease in amplitude and magnitude of velocity. B2 TE KE

River Valley High School Page 3 of 10 J2 H2 Physics 9749 2025 JC2 Preliminary Examinations Questions Answers Marks 3 (a) f v= m185.0 1780 330 = = A1 (b) 22 1 412 +=DS = 12.649 m Path difference = 12.649 – 12 18539.0 649.0= 5.3= M1 A1 (c) Since the two sources are in antiphase, the waves meet at D exactly in phase (Phase difference is 0 rad) and there is constructive interference. Hence a maximum intensity is detected. B1 A1 (d) Since path difference remains unchanged and there are two more changes in sound intensity, Path difference = (3.5 + 2) new = 5.5 new (new is the new wavelength) 5.5 new = 3.5  )18539.0(5.3)(5.5 = newf v fnew = 2797 Hz = 2800 Hz (3s.f.) B1 C1 A1 Questions Answers Marks 4 (a) Resistivity () is the proportionality constant between the dimensions of a specimen of a material and its resistance (that is constant at constant temperature) such that A LR = B1 (b) (i) N.B. If the soil is acidic, it reacts with copper and this produces an e.m.f. This occurs due to a galvanic reaction, where two dissimilar metals (in this case, copper plates) in an electrolyte (the acidic soil) create a voltage. V = 1.398 – 0.281 = 1.117 V I = 0.31x10-3 A R = V/I = 36