ID: Class: 12Subject: MathTopic: Application of DerivativeType: Short
Question:
A particle is moving along the curve \(6y = x^3 + 2\).
Find the points on the curve where the \(y\)-coordinate is changing 8 times as fast as the \(x\)-coordinate.
Official Solution
Explanation:
We start with the equation of the curve:
\[6y = x^3 + 2\]
Differentiating both sides with respect to time \(t\) gives:
\[6\frac{dy}{dt} = 3x^2 \frac{dx}{dt}\]
Dividing both sides by 3:
\[2\frac{dy}{dt} = x^2 \frac{dx}{dt}\]
According to the problem, the \(y\)-coordinate is changing 8 times as fast as the \(x\)-coordinate, i.e.,
\[\frac{dy}{dt} = 8\frac{dx}{dt}\]
Substituting this into the equation:
\[2(8\frac{dx}{dt}) = x^2 \frac{dx}{dt}\]
\[\Rightarrow 16\frac{dx}{dt} = x^2 \frac{dx}{dt}\]
Assuming \(\frac{dx}{dt} \ne 0\), we cancel it out. So :
\[x^2 = 16 \Rightarrow x = \pm 4\]
Now, we substitute these \(x\) values back into the original equation to find \(y\):
\[\]