A-LevelMathematicsMechanics9709/43 · May/June 2017 · Q68 Marks
A car of mass 1200 kg is travelling along a horizontal road.
- (i)(a)The engine of the car is working at 16 kW while the car is travelling at a constant speed of 40 m s⁻¹. Find the resistance to motion.[2]
- (i)(b)The power is now increased to 22.5 kW. Find the acceleration of the car at the instant it is travelling at a speed of 45 m s⁻¹.[3]
- (ii)It is given instead that the resistance to motion of the car is (590 + 2v) N when the speed of the car is v m s⁻¹. The car travels at a constant speed with the engine working at 16 kW. Find this speed.[3]
Mark scheme
Marking points from the official mark scheme (May/June 2017). The mark or mark type is shown in brackets.
- M1 Using P = Fv
- A1 Resistance is 400 N
- B1 F = 500
- M1 Applying Newton's Second Law
- A1 a = 1/12 = 0.0833 (ms⁻²)
- M1 Using P = Fv
- M1 Solving for v
- A1 v = 25 (ms⁻¹)
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