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Date May Specimen paper Marks available 5 Reference code SPM.2.AHL.TZ0.7
Level Additional Higher Level Paper Paper 2 Time zone Time zone 0
Command term Find Question number 7 Adapted from N/A

Question

Two ships, A and B , are observed from an origin O. Relative to O, their position vectors at time t hours after midday are given by

rA ( 4 3 ) + t ( 5 8 )

rB =  ( 7 3 ) + t ( 0 12 )

where distances are measured in kilometres.

Find the minimum distance between the two ships.

Markscheme

attempting to find rB − rA for example     (M1)

rB − rA =  ( 3 6 ) + t ( 5 4 )  

attempting to find |rB − rA|     M1

distance d ( t ) = ( 3 5 t ) 2 + ( 4 t 6 ) 2 ( = 41 t 2 78 t + 45 )       A1

using a graph to find the  d  − coordinate of the local minimum      M1

the minimum distance between the ships is 2.81 (km)  ( = 11 41 41 ( km ) )       A1

[5 marks]

Examiners report

[N/A]

Syllabus sections

Topic 3— Geometry and trigonometry » AHL 3.14—Vector equation of line
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Topic 3— Geometry and trigonometry

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