Air is being pumped into a balloon in the shape of a sphere so that its volume is increasing at a constant rate of 50 cm3s-1.
Find the rate at which the radius of the balloon is increasing when the radius is 10 cm.
Solution
The volume \(V\) of a sphere is given by \(V = \frac{4}{3}\pi r^3\).
Differentiate with respect to time \(t\):
\(\frac{dV}{dt} = 4\pi r^2 \frac{dr}{dt}\).
We know \(\frac{dV}{dt} = 50\) cm3s-1 and \(r = 10\) cm.
Substitute these values into the differentiated equation:
\(50 = 4\pi (10)^2 \frac{dr}{dt}\).
Simplify:
\(50 = 400\pi \frac{dr}{dt}\).
Solve for \(\frac{dr}{dt}\):
\(\frac{dr}{dt} = \frac{50}{400\pi} = \frac{1}{8\pi}\).
Thus, the rate at which the radius is increasing is \(\frac{1}{8\pi}\) cm/s or approximately 0.0398 cm/s.
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