Vectors, Scalars & Free Body force diagrams

Transcription

1 Vectors, Scalars & Free Body force diagrams Mark Scheme Level Subject Exam Board Topic Sub Topic Booklet Edexcel Physics GCSE(9-1) Forces & their Effects Vectors, Scalars & Free Body force diagrams Mark Scheme Time Allowed: Score: Percentage: 36 minutes /30 /100

2 1(ai) 150 m 1(aii) B at 7 s 1(aiii) 6 (s) 1(aiv) Substitution: 15 6 Allow ecf from 4(aiii) Must be 15 divided by their 4(aiii) Evaluation 2.5 (m/s 2 ) ECF allowed from first marking point ie evaluation of 15 divided by their answer from 4(aiii) Award 2 marks for correct answer, no working (2)

3 1(bi) (N) or 130 gains 1 mark Award 2 marks for correct answer, no working (2) 1(bii) 1(c) 550 (N) 539 (N) allow use of g = 9.8 N/kg (N) for use of g = 9.81N/kg Award mark for correct answer, no working An explanation linking (combined) mass is less smaller force required for same acceleration OR more acceleration from same force ignore references to weight, friction or backwards force ignore easier to accelerate as in stem less force needed (to accelerate) (2) (Total for 4 =10 marks)

4 2 (a) B 2 (b) A 0 N 2(c)(i) Substitution 1.2 = (20 13) / t 1.2 = 7 / t Transposition t = (20-13)/1.2 Evaluation 5.8 (s) substitution and transposition can be in either order t = 7/ (etc) Give full marks for correct answer, no working (3) 2(c) (ii) Substitution 1400 x 1.2 Evaluation 1700 (N) 1680 Allow full marks for correct answer with no working shown (2)

5 2 (c) (iii) An discussion to include three of the following points The tow rope does not have to support the weight of the car Tension is caused by accelerating force (plus frictional forces) Tension is 5700 N (in this situation ) Forces could be kept below 12,000N If acceleration is kept small forces are horizontal not vertical / only needs to overcome friction Force is needed to accelerate / resultant force is 0 at constant velocity Force to accelerate is 1700N Forces could be kept small If truck is driven gently/slowly Numerical justification using f = m x a (3) (Total for 4 = 10 marks)

6 3(a)(i) Answer B Mark 3(a)(ii) Answer vertical arrow, acting downward through the suitcase Mark Answer Additional guidance Mark 3(b)(i) substitution (KE =) award full marks for correct numerical answer without working answer 96 (J) allow (J) (2) Answer Additional guidance Mark 3(b)(ii) rearrange force = work done distance answer (force) = 15 (N) accept rearrangement with values subst., i.e. (force ) = award full marks for correct numerical answer without working (2) Answer Additional guidance Mark 3(c) An explanation that combines identification understanding (1 mark) and reasoning/justification understanding (1 mark): the work done is the same for walking and running because work done depends on force and distance only, not time allow energy for work done because work done time is power (2)

7 Answer Additional guidance Mark 3(d) rearrangement (height) = change in GPE (mass g) answer 2.2 (m) accept rearrangement with values, i.e. (h) = 264 (12 10) or = award full marks for correct numerical answer without working (2)

8 Moments Mark Scheme Level Subject Exam Board Topic Sub Topic Booklet Edexcel Physics GCSE(9-1) Forces & their Effects Moments Mark Scheme Time Allowed: Score: Percentage: 16 minutes /13 /100

9 1(a) Save My Exams! The Home of Revision Answer An explanation that combines identification application of knowledge (1 mark) and reasoning/justification application of understanding (3 marks): the gas cylinders have the same weight but cylinder A has the smallest area (that is in contact with the ground) the smaller the area, the greater the pressure (or reference Mark to P = F ) a hence cylinder A exerts a greater pressure on the ground (4) Answer Additional guidance Mark 1(b) rearrangement force up = (force down distance of force down from pivot)/distance of force up from pivot award full marks for correct numerical answer without working substitution into correct equation F = 0.40 answer 390 (N) (3)

10 *1(c) Indicative content Answers will be credited according to candidate's deployment of knowledge and understanding of the material in relation to the qualities and skills outlined in the generic mark scheme. The indicative content below is not prescriptive and candidates are not required to include all the material which is indicated as relevant. Additional content included in the response must be scientific and relevant. AO2 (6 marks) Mark The bubbles get bigger Molecules of gas in constant motion Molecules widely spaced and moving randomly Molecules impact on surface of bubble/liquid molecules Average of impacts produces gas pressure Pressure is due to rate at which gas particles collide with liquid molecules/bubble surface Liquid pressure decreases as bubble rises P 1 V 1 = P 2 V 2 If pressure decreases, volume of bubble will increase/volume of bubble must increase to give a decrease in pressure As volume increases, rate at which particles collide with surface of bubble decreases (6) Level Mark Descriptor 0 No awardable content. Level The explanation attempts to link and apply knowledge and understanding of scientific ideas, flawed or simplistic connections made between elements in the context of the question. (AO2) Lines of reasoning are unsupported or unclear. (AO2) Level The explanation is mostly supported through linkage and application of knowledge and understanding of scientific ideas, some logical connections made between elements in the context of the question. (AO2) Lines of reasoning mostly supported through the application of relevant evidence. (AO2) Level The explanation is supported throughout by linkage and application of knowledge and understanding of scientific ideas, logical connections made between elements in the context of the question. (AO2) Lines of reasoning are supported by sustained application of relevant evidence. (AO2)