Differentiation - Connected Rates of Change

Differentiation - Connected Rates of Change

A container in the shape of a hemi-sphere of radius \(8\) cm is completely filled with water. The water is then poured into an empty inverted right circular cone of radius \(8\) cm and height \(16\) cm at a steady rate.

  1. Given that all the water is poured in \(5\frac{1}{3}\) minutes and that \(V\) cm\(^3\) represents the amount of water in the cone at any time, \(t\) show that \(\dfrac{\mathrm{d}V}{\mathrm{d}t}=64\pi\) cm\(^3\)/min.
  1. Leaving your answers in terms of \(\pi\),
    1. Express the volume of water in the cone in terms of \(h\), where \(h\) is the depth of water in the cone.
    2. Find the rate of change of the height of water level in the circular cone, when the height of the water level in the cone is \(6\) cm.

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Answer:(a) \(64\pi\text{ cm}^3\text{ min}^{-1}\) (b)(i) \(V=\frac{\pi h^3}{12}\text{ cm}^3\) (b)(ii) \(\frac{\mathrm dh}{\mathrm dt}=\frac{64}{9}\text{ cm min}^{-1}\)

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