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Date May 2022 Marks available 5 Reference code 22M.2.AHL.TZ2.6
Level Additional Higher Level Paper Paper 2 Time zone Time zone 2
Command term Determine Question number 6 Adapted from N/A

Question

The following diagram shows the curve x236+y-4216=1, where hy4.

The curve from point Q to point B is rotated 360° about the y-axis to form the interior surface of a bowl. The rectangle OPQR, of height hcm, is rotated 360° about the y-axis to form a solid base.

The bowl is assumed to have negligible thickness.

Given that the interior volume of the bowl is to be 285cm3, determine the height of the base.

Markscheme

attempts to express x2 in terms of y         (M1)

V=πh4361-y-4216dy          A1


Note: Correct limits are required.

 

Attempts to solve πh4361-y-4216dy=285 for h         (M1)

Note: Award M1 for attempting to solve 36πh348-h24+83=285 or equivalent for h.


h=0.7926

h=0.793 (cm)          A2

 

[5 marks]

Examiners report

This question was a struggle for many candidates. To start with, many candidates had difficulty understanding the diagram. Some candidates tried to include the base in their equation. 

Because of this confusion, the question was poorly attempted. Some only received one mark for rearranging the equation to make x2 the subject but were unable to set the correct definite integral with correct terminals. Again, many candidates tried to solve by hand instead of using their GDC. The correct answer was not seen that often.

Those candidates who recognised that the volume was around the y -axis and used their GDC to solve, usually achieved full marks for this question.

Syllabus sections

Topic 5 —Calculus » AHL 5.17—Areas under curve onto y-axis, volume of revolution (about x and y axes)
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Topic 5 —Calculus

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