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A-LevelMathematicsMechanics9709/42 · May/June 2019 · Q67 Marks

A car has mass 1000 kg. When the car is travelling at a steady speed of v m s⁻¹, where v > 2, the resistance to motion of the car is (Av + B) N, where A and B are constants. The car can travel along a horizontal road at a steady speed of 18 m s⁻¹ when its engine is working at 36 kW. The car can travel up a hill inclined at an angle of θ to the horizontal, where sin θ = 0.05, at a steady speed of 12 m s⁻¹ when its engine is working at 21 kW. Find A and B.

  1. A car has mass 1000 kg. When the car is travelling at a steady speed of v m s⁻¹, where v > 2, the resistance to motion of the car is (Av + B) N, where A and B are constants. The car can travel along a horizontal road at a steady speed of 18 m s⁻¹ when its engine is working at 36 kW. The car can travel up a hill inclined at an angle of θ to the horizontal, where sin θ = 0.05, at a steady speed of 12 m s⁻¹ when its engine is working at 21 kW. Find A and B.[7]

Mark scheme

Marking points from the official mark scheme (May/June 2019). The mark or mark type is shown in brackets.

  1. [B1] DF = P/v in either case
  2. [M1] Use DF = resistance (case 1)
  3. [A1] Correct equation, unsimplified
  4. [M1] Use DF = resistance + weight component (case 2)
  5. [A1] Correct equation, unsimplified
  6. [DM1] Solve two simultaneous equations in A and B only for A or B Dependent on both previous M1's
  7. [A1] Both correct

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About this question

Topic
Mechanics, A-Level Mathematics (syllabus 9709). Structured question, 7 marks.
Source
A-Level Mathematics, May/June 2019 Paper 4 Variant 2, question 6.

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