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.
- 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.
- [B1] DF = P/v in either case
- [M1] Use DF = resistance (case 1)
- [A1] Correct equation, unsimplified
- [M1] Use DF = resistance + weight component (case 2)
- [A1] Correct equation, unsimplified
- [DM1] Solve two simultaneous equations in A and B only for A or B Dependent on both previous M1's
- [A1] Both correct
Write your answer and get it marked
On Oracle Prep you can write or photograph your own answer and have it marked by AI against this mark scheme, with feedback on what you missed.
Sign up free →