Physics (AS & A Level) · Oct / Nov 2016 · Paper 21 · Question 3
9702
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3(a)[1]
force/load is proportional to extension/compression (provided proportionality limit is not exceeded) [1]
3(b)(i)[2]
k = F / x or k = gradient k = 600 N m–1 [2]
3(b)(ii)[2]
(W =) ½kx2 or (W =) ½Fx or (W =) area under graph (W =) 0.5 × 600 × (0.040) 2 = 0.48 J or (W =) 0.5 × 24 × 0.040 = 0.48 J [2]
3(b)(iii)[5]
1. (EK =) ½mv2 = ½ × 0.025 × 6.02 = 0.45 J [2]
2. (work done against resistive force =) 0.48 – 0.45 [= 0.03(0) J] average resistive force = 0.030 / 0.040 = 0.75 N [3]
3(b)(iv)[2]
efficiency = [useful energy out / total energy in] (×100) = [0.45 / 0.48] (×100) = 0.94 or 94% [2]
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