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.
The volume of water is increasing at a constant rate of 0.0008 m3s−1.
Find an expression for the volume of water V (m3) in the trough in terms of θ.
Calculate dθdt when θ=π3.
Markscheme
* This question is from an exam for a previous syllabus, and may contain minor differences in marking or structure.
area of segment =12×0.52×(θ−sinθ) M1A1
V=area of segment×10
V=54(θ−sinθ) A1
[3 marks]
METHOD 1
dVdt=54(1−cosθ)dθdt M1A1
0.0008=54(1−cosπ3)dθdt (M1)
dθdt=0.00128 (rads−1) A1
METHOD 2
dθdt=dθdV×dVdt (M1)
dVdθ=54(1−cosθ) A1
dθdt=4×0.00085(1−cosπ3) (M1)
dθdt=0.00128(43125)(rad s−1) A1
[4 marks]