A-LevelMathematicsMechanics9709/42 · Feb/Mar 2020 · Q26 Marks

A particle P of mass 0.4 kg is on a rough horizontal floor. The coefficient of friction between P and the floor is μ. A force of magnitude 3 N is applied to P upwards at an angle α above the horizontal, where tan α = 3/4. The particle is initially at rest and accelerates at 2 ms⁻².

(a)Find the time it takes for P to travel a distance of 1.44 m from its starting point.[2]
(b)Find μ.[4]

Mark scheme

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

[M1] For using a complete method which would lead to an equation for finding a value of t such as s = ut + ½ at² with u = 0, s = 1.44 and a = 2
[A1]
[B1]
[M1] Use Newton's 2nd law, 3 terms, to find F.
[M1] Use of μ = F/R
[A1] Allow μ = 8/11

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Topic: Mechanics, A-Level Mathematics (syllabus 9709). Structured question, 6 marks.
Source: A-Level Mathematics, Feb/Mar 2020 Paper 4 Variant 2, question 2.

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