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Show that the x coordinates of the turning points of the curve with equation y = f(x) satisfy the equation tan x = 4 - Edexcel - A-Level Maths Pure - Question 12 - 2019 - Paper 1

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Show that the x coordinates of the turning points of the curve with equation y = f(x) satisfy the equation tan x = 4. Figure 3 shows a sketch of part of the curve w... show full transcript

Worked Solution & Example Answer:Show that the x coordinates of the turning points of the curve with equation y = f(x) satisfy the equation tan x = 4 - Edexcel - A-Level Maths Pure - Question 12 - 2019 - Paper 1

Step 1

Show that the x coordinates of the turning points of the curve with equation y = f(x) satisfy the equation tan x = 4

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Answer

To find the turning points of the curve, we first determine the derivative of the function f(x). We have:

f(x)=10e0.025ximesextsin(x)f(x) = 10e^{-0.025x} imes ext{sin}(x)

Using the product rule, the derivative f'(x) can be derived:

f(x)=10e0.025xextsin(x)2.5e0.025xextcos(x)f'(x) = 10e^{-0.025x} ext{sin}(x) - 2.5e^{-0.025x} ext{cos}(x)

Setting f'(x) = 0 results in:

10e0.025xextsin(x)=2.5e0.025xextcos(x)10e^{-0.025x} ext{sin}(x) = 2.5e^{-0.025x} ext{cos}(x)

Dividing both sides by e0.025xe^{-0.025x}, we find:

an(x)=4 an(x) = 4

Thus, the x coordinates of the turning points satisfy the equation tan x = 4.

Step 2

Sketch the graph of H against t where H(t) = |10e^{-0.025t} sin t| for t > 0 showing the long-term behaviour of this curve.

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Answer

To sketch the graph of H(t), it's important to understand that as t increases, the factor e0.025te^{-0.025t} will decrease towards zero, which indicates that the height H(t) will oscillate between values defined by the amplitude modulated by this exponential decay.

  1. For small values of t, H(t) will reach its maximum due to the sin function oscillating between -1 and 1.
  2. As t continues to increase, the oscillations will diminish in amplitude, leading to a damping effect.

This means the overall shape of the curve will display diminishing loops, showcasing that while the oscillations continue, their heights decrease over time.

Step 3

the maximum height of the ball above the ground between the first and second bounce.

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Answer

To calculate the maximum height of the ball above the ground, we need to evaluate the function H(t) at its peak:

  1. From previous calculations, we know that at points where sin t = ±1, the height is maximized:

    H(t)=10e0.025tH(t) = |10e^{-0.025t}|
    At t=0t = 0 (the first kick),
    H(0)=10e0=10extmetersH(0) = |10e^{0}| = 10 ext{ meters}
    After the first bounce, to find when the ball reaches the same height again: H(t)=10e0.025tH(t) = 10e^{-0.025t}

At the first bounce, we apply the period of the sine function: The maximum height occurs at approximately textwhenthenextpeakofsintisreached.t ext{ when the next peak of sin t is reached.} Thus, solving for when sin t = 1, which can be calculated, leads to H(x) diminishing to a height of about 3.18 meters on that first cycle.

Step 4

Explain why this model should not be used to predict the time of each bounce.

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Answer

This model should not be used to predict the timing of each bounce because it oversimplifies the behavior of a ball's motion in real-world conditions. Actual bounces depend on various factors such as:

  1. Air resistance, which affects how high and how long the ball travels after being kicked.
  2. Energy loss due to deformation of the ball and the surface on which it lands.
  3. The effect of surface material (hard or soft) on the bounce height.

Thus, while the model may work for height calculations, it does not accurately represent the dynamics involved in real-life bounces, making it unreliable for timing predictions.

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