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Date May 2017 Marks available 3 Reference code 17M.2.AHL.TZ1.H_8
Level Additional Higher Level Paper Paper 2 Time zone Time zone 1
Command term Find Question number H_8 Adapted from N/A

Question

A water trough which is 10 metres long has a uniform cross-section in the shape of a semicircle with radius 0.5 metres. It is partly filled with water as shown in the following diagram of the cross-section. The centre of the circle is O and the angle KOL is θ radians.

M17/5/MATHL/HP2/ENG/TZ1/08

The volume of water is increasing at a constant rate of 0.0008   m 3 s 1 .

Find an expression for the volume of water V   ( m 3 ) in the trough in terms of θ .

[3]
a.

Calculate d θ d t when θ = π 3 .

[4]
b.

Markscheme

* This question is from an exam for a previous syllabus, and may contain minor differences in marking or structure.

area of segment = 1 2 × 0.5 2 × ( θ sin θ )      M1A1

V = area of segment × 10

V = 5 4 ( θ sin θ )      A1

[3 marks]

a.

METHOD 1

d V d t = 5 4 ( 1 cos θ ) d θ d t      M1A1

0.0008 = 5 4 ( 1 cos π 3 ) d θ d t      (M1)

d θ d t = 0.00128   ( rad s 1 )      A1

METHOD 2

d θ d t = d θ d V × d V d t      (M1)

d V d θ = 5 4 ( 1 cos θ )      A1

d θ d t = 4 × 0.0008 5 ( 1 cos π 3 )      (M1)

d θ d t = 0.00128 ( 4 3125 ) ( rad  s 1 )      A1

[4 marks]

b.

Examiners report

[N/A]
a.
[N/A]
b.

Syllabus sections

Topic 5—Calculus » SL 5.3—Differentiating polynomials, n E Z
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