A-LevelMathematicsMechanics9709/41 · May/June 2020 · Q25 Marks

A car of mass 1800 kg is towing a trailer of mass 400 kg along a straight horizontal road. The car and trailer are connected by a light rigid tow-bar. The car is accelerating at 1.5 m s⁻². There are constant resistance forces of 250 N on the car and 100 N on the trailer.

(a)Find the tension in the tow-bar.[2]
(b)Find the power of the engine of the car at the instant when the speed is 20 m s⁻¹.[3]

Mark scheme

Marking points from the official mark scheme (May/June 2020). The mark or mark type is shown in brackets.

[M1] [T-100=400×1.5]
[A1] T=700 N
[M1] F-250-100=2200 × 1.5 (F = 3650 N) (M1 for using Newton's second law for the system or for the car using the result from 2(a))
[M1] For use of power = Fv
[A1] 73 000 W or 73 kW

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Topic: Mechanics, A-Level Mathematics (syllabus 9709). Structured question, 5 marks.
Source: A-Level Mathematics, May/June 2020 Paper 4 Variant 1, question 2.

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