(ACJC) 2024 J2 H2 Physics Prelim P2 Solution

Anglo-Chinese Junior College 2024 J2 Preliminary Exam Paper 2 Guide H2 (9749) Physics JC2 2024 Page 1 of 7 Qn Suggested Answer 1 (a) Precision is defined as a measure of how close the experimental values are to each other. Accuracy is defined as a measure of how close the experimental values are to the true value of the physical quantity. (b) ( ) 222 -2 22 4 50 0 104 9 78933 m s1 42 Lg T . ..  − = = = 2g L T g L T    = +  0 2 0 02 9 78933 0 1770450 0 1 42g  = +  = .. .... = ± 0.2 m s−2 (1 s.f.) g = 9.8 ± 0.2 m s−2 (c) There is error due to human reaction time . Taking a large number of oscillations will reduce the fractional/percentage uncertainty of the measurement of time. The absolute uncertainty is the same but taking more oscillations reduces the effect in the calculation of T. (ΔT = Δt / n where Δt = ± 0.2 – 0.4 s (human reaction time) and n is the number of oscillations.) 2 (a)(i) Taking upwards as positive, 22 22 2 0 2( 9.81)(27) v u as u =+ = + − -1 23.02 23 m s (2 s.f.) (shown) u = =

Anglo-Chinese Junior College 2024 J2 Preliminary Exam Paper 2 Guide H2 (9749) Physics JC2 2024 Page 2 of 7 (a)(ii) Straight line with negative gradient. Initial velocity of 23 m s−1. Max height at 2.34 s. Graph stops at 6.0 s with velocity of -35.9 m s−1. max height -1 0 ( 23) 2.34 s9.81 At 6.0 s 23 (9.81)(6.0) 35.9 m s vu gt vut g t v u at − = − − −= = = = = + = − =− (a)(iii) Steeper slope before v = 0. Gentler slope after v = 0. Gradient at v = 0 should be parallel to graph in (a)(ii). (b) GPE linear with negative gradient. EPE parabolic shape starting from x0. KE shape and correct KE value at x0 and xs (TE is constant). 3 (a) The resultant force acting on the object must be zero. The resultant torque about any axis is zero. (b) Taking moments about the hinge, ( ) ( ) ( ) 3 1.32 0.80052 3 1.32 47.5 0.80052 TW W     =           =       70.2 NW = 70.2 7.2 kg (2 s.f.)9.81m==

Anglo-Chinese Junior College 2024 J2 Preliminary Exam Paper 2 Guide H2 (9749) Physics JC2 2024 Page 3 of 7 (c) The tension in the cables has a horizontal component, while the weight has only vertical component. For the canopy to be in equilibrium, there must be a horizontal c