4.03: Related rates in a cone

0606/13/M/J/26 — Question 6 · 6 marks

Water is poured into an inverted cone. The semi-vertical angle is \(30^\circ\) and \(\tan30^\circ=1/\sqrt3\).
(a)
Show that the volume of water of depth \(h\) is \(V=\dfrac{\pi}{9}h^3\).
[2]
(b)
Given \(\dfrac{\mathrm dV}{\mathrm dt}=50\), find \(\dfrac{\mathrm dh}{\mathrm dt}\) when \(h=60\), giving the answer in terms of \(\pi\).
[4]
Official diagram for Question 6