RVHS H2 Physics P3 Soln

River Valley High School Page 1 of 12 J2 H2 Physics 9749 Preliminary Examinations RVHS JC2 H2 Physics Preliminary Examinations Paper 3 Mark Scheme Questions Answers Marks 1 (a) Repeated readings with error of different magnitude and sign. OR Repeated readings with scatter of readings about a mean value. By plotting a graph and drawing a line of best fit for the points/can be reduced by averaging B1 B1 (b) Units of 𝑘𝑘𝑟𝑟3(𝑝𝑝1−𝑝𝑝2) 𝑙𝑙 � 𝑀𝑀 𝑅𝑅𝑅𝑅 = 𝑚𝑚3𝑃𝑃𝑃𝑃 𝑚𝑚 � 𝑘𝑘𝑘𝑘 𝑚𝑚𝑚𝑚 𝑙𝑙−1 𝐽𝐽 𝐾𝐾−1 𝑚𝑚𝑚𝑚 𝑙𝑙−1𝐾𝐾 = 𝑘𝑘𝑘𝑘𝑘𝑘𝑠𝑠−2� 𝑘𝑘𝑘𝑘 𝑠𝑠2 𝑘𝑘𝑘𝑘𝑚𝑚2 = 𝑘𝑘𝑘𝑘𝑠𝑠−1 (c) (i) Density = m/V m = density x V = density x π(D 2 / 4 ) L = ( 8 . 9 6 ) x π ( 6 . 02 /4) L = 7093.46 g = 7.09346 kg ∆m/m = 2∆D/D + ∆L/L = (2(0.1)/(6.0) + (0.1/28.0) = 0.0369 ∆m = m(2∆D/D + ∆L/L) = (7093.46)(0.0369) = 0.262 kg 7.1 +/- 0.3 kg (Correct s.f.) M1 M1 A1 A1 (ii) Same measurements, but smaller absolute uncertainties, so percentage uncertainty is smaller B1 Questions Answers Marks 2 (a) apply equation of motion 𝑣𝑣 = 𝑢𝑢 + 𝑎𝑎𝑎𝑎 vertically, we get −5 = +5 − 9.81𝑎𝑎 for substitution M1 𝑎𝑎 = 1.019 s for intermediate value A1 (b) 20 1.019 = 19.62 m s-1 B1 Alternative, Using 𝑣𝑣𝑦𝑦 = 𝑢𝑢0 + 𝑎𝑎𝑎𝑎 and substituting 𝑎𝑎 = 𝑥𝑥 𝑣𝑣𝑥𝑥 , we get 𝒗𝒗𝒚𝒚 = 𝑢𝑢0 − 𝑘𝑘 1 𝑣𝑣𝑥𝑥 𝒙𝒙. So gradient = − 1 2 = − 9.81 𝑣𝑣𝑥𝑥

River Valley High School Page 2 of 12 J2 H2 Physics 9749 Preliminary Examinations (c) 𝑎𝑎𝑎𝑎𝑡𝑡 𝜃𝜃 = 5.0 19.62 M1 𝜃𝜃 = 14.3𝑚𝑚 A1 (d) x-intercept at (20,0) (because at maximum height 𝑣𝑣𝑦𝑦 = 0) y-intercept above 5 (because with θ < 45o to increase range , θ needs to increase, and v sinθ needs to increase.) Example: Extra note As θ increase, and 𝑣𝑣𝑥𝑥 =v cosθ decreases. So gradient increases. B1 3 (a) The moment of a force is equal to the product of the force and the perpendicular distance of the line of action of the force from the pivot. It is the turning effect of a force. B1 (b) (i) -15 -10 -5 0 5 10 15 0 2 4 6 8 10 12 14 16 18 20

River Valley High School Page 3 of 12 J2 H2 Physics 9749 Preliminary Examinations Take moments about the hinge, (400)( sin60) 2000( sin60) sin30( )2 3810 N L L TL T += = B1 C1 A1

River Valley High School Page 4 of 12 J2 H2 Physics 9749 Preliminary Examinations (ii) (c) The direction of all forces remain unchange since the load remains submerged in water at the same location. The upthrust acting on the load will reduce the tension in the rope. Since the horizontal component of the tension reduces, the force by wall on rod also reduces. This will result in a lower value of force by rod on wall. B1 (directi on) B1 (magnit ude) Questions Answers Marks total weight of rod and load ON rod tension of rope ON rod f