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Mike, an amateur astronomer who lives in the South of England, wants to know how the number of hours of darkness changes through the year - AQA - A-Level Maths Mechanics - Question 8 - 2020 - Paper 1

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Mike, an amateur astronomer who lives in the South of England, wants to know how the number of hours of darkness changes through the year. On various days between F... show full transcript

Worked Solution & Example Answer:Mike, an amateur astronomer who lives in the South of England, wants to know how the number of hours of darkness changes through the year - AQA - A-Level Maths Mechanics - Question 8 - 2020 - Paper 1

Step 1

Find the minimum number of hours of darkness predicted by Mike's model.

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Answer

To find the minimum of the function, we note that the sine function reaches its minimum value of -1. Plugging this into the equation:

H=3.87extsin(2π(t+101.75)365)+11.7H = 3.87 \, ext{sin} \left( \frac{2\pi(t + 101.75)}{365} \right) + 11.7

The minimum occurs when:

H=3.87(1)+11.7=11.73.87=7.83H = 3.87(-1) + 11.7 = 11.7 - 3.87 = 7.83

To convert hours into minutes, we have:

0.83hours=0.83×6050 minutes0.83 \, hours = 0.83 \times 60 \approx 50 \text{ minutes}

Thus, the minimum number of hours of darkness is approximately 7 hours and 50 minutes.

Step 2

Find the maximum number of consecutive days where the number of hours of darkness predicted by Mike's model exceeds 14.

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Answer

Set the equation for H greater than 14:

3.87extsin(2π(t+101.75)365)+11.7>143.87 \, ext{sin} \left( \frac{2\pi(t + 101.75)}{365} \right) + 11.7 > 14

This simplifies to:

3.87extsin(2π(t+101.75)365)>2.33.87 \, ext{sin} \left( \frac{2\pi(t + 101.75)}{365} \right) > 2.3

Dividing through by 3.87, we get:

sin(2π(t+101.75)365)>0.593\text{sin} \left( \frac{2\pi(t + 101.75)}{365} \right) > 0.593

Finding the angles related to this sine value gives:

2π(t+101.75)365=arcsin(0.593)\frac{2\pi(t + 101.75)}{365} = arcsin(0.593)

Calculating gives values of approximately ( t \approx 300.22 ) and ( t \approx 408.77 ).

Thus, the consecutive days can be calculated as:

Days=408300=108 days\text{Days} = 408 - 300 = 108 \text{ days}.

Step 3

Explain whether Sofia's refinement is appropriate.

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Answer

Sofia's refinement aims to increase the amplitude of the graph by raising the 3.87 value in Mike's model. While this would increase the range of the graph and the variability in darkness hours, Sofia's data does not suggest such fluctuations. Thus, her refinement may not be appropriate, as it could misrepresent the relatively stable trend in her recorded hours of darkness, leading to a less accurate model.

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