Curve motion: find x-coordinate

Given a curve equation and information about dy/dt and dx/dt, find the x-coordinate where a specific rate condition holds.

3 questions · Standard +0.3

1.07r Chain rule: dy/dx = dy/du * du/dx and connected rates
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CAIE P1 2024 June Q10
10 marks Standard +0.3
The equation of a curve is \(y = (5-2x)^{\frac{1}{2}} + 5\) for \(x < \frac{5}{2}\).
  1. A point \(P\) is moving along the curve in such a way that the \(y\)-coordinate of point \(P\) is decreasing at 5 units per second. Find the rate at which the \(x\)-coordinate of point \(P\) is increasing when \(y = 32\). [4]
  2. Point \(A\) on the curve has \(y\)-coordinate 32. Point \(B\) on the curve is such that the gradient of the curve at \(B\) is \(-3\). Find the equation of the perpendicular bisector of \(AB\). Give your answer in the form \(ax + by + c = 0\), where \(a\), \(b\) and \(c\) are integers. [6]
CAIE P1 2014 November Q4
6 marks Standard +0.3
A curve has equation \(y = \frac{12}{5 - 2x}\).
  1. Find \(\frac{dy}{dx}\). [2]
A point moves along this curve. As the point passes through \(A\), the \(x\)-coordinate is increasing at a rate of 0.15 units per second and the \(y\)-coordinate is increasing at a rate of 0.4 units per second.
  1. Find the possible \(x\)-coordinates of \(A\). [4]
CAIE P3 2018 June Q9
8 marks Standard +0.3
A curve is such that \(\frac{\mathrm{d}y}{\mathrm{d}x} = \sqrt{(4x + 1)}\) and \((2, 5)\) is a point on the curve.
  1. Find the equation of the curve. [4]
  2. A point \(P\) moves along the curve in such a way that the \(y\)-coordinate is increasing at a constant rate of 0.06 units per second. Find the rate of change of the \(x\)-coordinate when \(P\) passes through \((2, 5)\). [2]
  3. Show that \(\frac{\mathrm{d}^2y}{\mathrm{d}x^2} \times \frac{\mathrm{d}y}{\mathrm{d}x}\) is constant. [2]