ADVANCED SUBSIDIARY (AS) General Certificate of Education Physics Assessment Unit AS 1. assessing. Module 1: Forces, Energy and Electricity

Transcription

1 ADVANCED SUBSIDIARY (AS) General Certificate of Education 2015 Physics Assessment Unit AS 1 assessing Module 1: Fces, Energy and Electricity [AY111] THURSDAY 11 JUNE, MORNING MARK SCHEME F

2 Subject-specific Instructions In numerical problems, the marks f the intermediate steps shown in the mark scheme are f the benefit of candidates who do not obtain the final crect answer. A crect answer and unit, if obtained from a valid starting-point, gets full credit, even if all the intermediate steps are not shown. It is not necessary to quote crect units f intermediate numerical quantities. Note that this crect answer rule does not apply f fmal proofs and derivations, which must be valid in all stages to obtain full credit. Do not reward wrong physics. No credit is given f consistent substitution of numerical data, subsequent arithmetic, in a physically increct equation. However, answers to subsequent stages of questions that are consistent with an earlier increct numerical answer, and are based on physically crect equation, must gain full credit. Designate this by writing ECF (Err Carried Fward) by your text marks. The nmal penalty f an arithmetical and/ unit err is to lose the mark(s) f the answer/unit line. Substitution errs lose both the substitution and answer marks, but 10 n errs (e.g. writing 550 nm as m) count only as arithmetical slips and lose the answer mark F 2 [Turn over

3 1 (a) Energy can neither be created destroyed; it can only be converted from one fm to another. [1] (b) Power is the rate at which wk is done [1] Power = (wk done)/time (c) ((In 1 second), energy converted from PE to electrical = J) PE = mgh = ( m water ) [1] m water moving per second = ( )/(6 9.81) subs = value [1] = kg (2s.f.) [1] [3] 5 sf mark is independent F 3

4 2 (a) (i) 200 km h # 1000 = 3600 = m s 1 [1] (ii) v/ms t/s Crect shape of graph [1] Crect data on axes [1] [2] (iii) Distance = area between graph and time axes [1] 1 1 = _ # 12 # i + ^ 20 # 55.6h + _ # 2 8 # 55.6i = 1668m [1] [2] SE = 6000 m [1]/[2] (b) (i) Acceleration is proptional to (resultant) fce and inversely proptional to mass. [1] Acceleration is in the same direction as fce [1] [2] Newton s 2nd Law states that the rate of change of momentum of an object is directly proptional to the applied fce and [1] takes place in the same direction in which this fce acts. [1] F = ma with terms defined [1] F and a in same direction [1] (ii) F nett = ma 8000 [200 + (1480gsin12)] = 1480a subs [1] a = 3.23ms 2 [1] [2] (iii) s = [ut at 2 ] spts car [ut at 2 ] heavy car eqn [1] 180 = t = 2 ( )t subs [1] t = 16.7s [1] [3] ecf f a from (b)(ii) F 4 [Turn over

5 3 (a) Diagram of set-up and labels to show: Clear indication of distance through which object falls (using a metre ruler). Clear indication of how time f which object falls is measured. 2 x [ 2 1 ] round down [1] Or if data logging method used: Card length and light gate(s) (b) Measure the distance through which the object falls, s, using a metre ruler [1] (The crect distance must be marked on diagram explained specifically) Measure time, t, taken f ball to fall through distance s using an electronic timing system/light gates [1] [2] Or if data logging method used: Length of card using a metre rule/calipers [1] Times determined using the electronics with detail in method [1] Methods of measuring should be consistent with method used. (c) Plot a graph of s (y-axis) against t 2 (x-axis) [1] g = 2 gradient [1] Plot a graph of 2s (y-axis) against t 2 (x-axis) g = gradient Plot a graph of s (y-axis) against t 2 /2 (x-axis) g = gradient Calculate g f each set of data using g = 2s/t 2 Average g values Or if data logging method used: g obtained from v u [1] t Where u and v are average speeds and t the time between them [1] [2] (d) Repeat experiment f each height. Find average time. [1] Or if data logging method used: Repeat (f consistency) and average F 5

6 Quality of written communication 2 marks The candidate expresses ideas clearly and fluently, through well-linked sentences and paragraphs. Arguments are generally relevant and well structured. There are few errs of grammar, punctuation and spelling. 1 mark The candidate expresses ideas clearly, if not always fluently. Arguments may sometimes stray from the point. There are some errs in grammar, punctuation and spelling, but not such as to suggest a weakness in these areas. 0 marks The candidate expresses ideas satisfactily, but without precision. Arguments may be of doubtful relevance obscurely presented. Errs in grammar, punctuation and spelling are sufficiently intrusive to disrupt the understanding of the passage. [2] F 6 [Turn over

7 4 (a) Parabolic [1] (b) Hizontal component = v cos 37 (= 0.8 v) Vertical component = v sin37 (= 0.6 v) [1] (c) (i) e.c.f. [6] Range = hizontal velocity (ecf (b)) time of flight 8.31 = 9.21cos37 t [1] 8.31 t = 9.21cos 37% = 1.13s [1] [2] ecf from (b) use of time to reach max height 2 (ii) Find vertical component of velocity v v at t = 0.50s: v v = u v + a v t = 9.21sin37 + ( ) = 0.64ms 1 [1] Find hizontal component of velocity v h at t = 0.50s: v h = u h + a h t = 9.21cos = 7.36ms 1 ecf (components) [1] Find resultant velocity V and angle to hizontal: V = ( ) = 7.39ms 1 ecf* (components) [1] = tan b l = 4.97 above hizontal ecf* (components) [1] [4] 7.36 No credit f θ > 37 ecf from (b) 8 θ V 7.36m s m s F 7

8 5 (a) 2 errs/omissions: when an object is in (rotational) equilibrium [1] about the same point [1] [2] (b) (i) (F B 0.068) = ( ) + (1.5g 0.37) [1] [1] crect subs each side [2] F B = 150 N [1] [3] Any moment calculation [1]/[3] (ii) 1. F E = (F B g) F E = (F B 25 W) [1] Accept crect principle of moments alternatives. 2. Use expression to calculate F E F E = [ ( )] F E = N [1] ecf from (b)(i) F 8 [Turn over

9 6 (a) (i) The ratio of the stress (in the material) to the strain (of the material). [1] E = if terms are crectly defined (ii) (1Pa =) kg m 1 s 2 [1] (b) (i) Tension in each wire = (41g)/2 = 201N [1] (ii) ni = /E = ( )/( ) eqn subs [1] = ([ 1] if a unit is given) [1] [2] (iii) x ni = l = ( ) 5 ecf (ii) = m = 2.08mm [1] (iv) Since the seat is hizontal, cu = ni x cu = x ni = 2.08 mm [1] Fl A cu = (equation in this fm) [1] xe 201 # 5 ecf * (tension) = 2.08 # # 1.17 # = ( ) value subs [1] 1 d cu = 4A 2 b l ecf* (area) r # # - 2 = c m r = m = 2.29mm [1] [4] ecf from(b)(i) and (iii) F 9

10 7 (a) The resistivity of a material is numerically equal to the resistance of a 1 metre sample of the material with (cross-sectional) area 1m 2. [1] (b) (Tungsten is a) conduct (Tungsten has) me charge carriers Any 2 of 3 [2] Charge carriers flow freely (c) (i) ρ / Ωm A B C T/K Section AB of graph [1] Section BC of graph [1] [2] (ii) Transition Critical temperature [1] (iii) Greater efficiency Reduced expense incurred in cooling [1] F 10 [Turn over

11 8 (a) The electromotive fce of a source is the energy converted (from chemical) to electrical when unit charge passes (through it). [1] (b) (i) emf > tpd emf = tpd emf < tpd Switch Open Switch Closed both crect [1] (ii) e.m.f. = intercept on x-axis = 1.80 V [1] (iii) Calculate gradient using large triangle [1] Internal resistance = 1 gradient = 0.22 ± 0.02 [1] [2] Or Use of E = Ir + V and crect substitution [1] to obtain r [1] ecf (ii) 5 Negative resistance, penalty [ 1] F 11

12 9 (a) Resistance of 6 and 2 in parallel = 1.5 [1] Resistance of netwk of 4 resists = ( ) = 5 [1] R Resistance of 1, 5 and R in series = 10 [1] Hence R = (10 5 1) = 4 [1] [4] 15 (b) Current drawn from battery = = 1.2 A [1] 12.5 Current = 0.9 A (through 2 resist) [1] Power dissipated in R = I 2 R = 1.62 W [1] [3] 7 (ecf f I) 10 # (a) V out in bright = subs [1] = 0.48V [1] [2] (b) Voltage across 300 resist = 9V [1] Thus resistance of LDR and mot combination = 200 [1] R m = : - D ; 1 + = E ecf* Rm 200 subs [1] R m = 1000 [1] [4] 6 Penalty [ 1] f negative resistance Total F 12 [Turn over