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A motorised scooter is travelling along a straight path with velocity $v \text{ m s}^{-1}$ over time $t$ seconds as shown by the following graph - AQA - A-Level Maths Mechanics - Question 14 - 2021 - Paper 2

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A motorised scooter is travelling along a straight path with velocity $v \text{ m s}^{-1}$ over time $t$ seconds as shown by the following graph. Noosha says that, ... show full transcript

Worked Solution & Example Answer:A motorised scooter is travelling along a straight path with velocity $v \text{ m s}^{-1}$ over time $t$ seconds as shown by the following graph - AQA - A-Level Maths Mechanics - Question 14 - 2021 - Paper 2

Step 1

Determine the area under the curve between $12 \leq t \leq 36$

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Answer

To find the distance travelled by the scooter in the time interval from t=12t=12 to t=36t=36, we will calculate the area under the velocity curve using trapezoidal approximation. The area will be calculated as the sum of four trapezoids:

  1. Trapezium 1: For the interval [12,20][12, 20]:

    • Height 1 = 5.25.2
    • Height 2 = 6.26.2
    • Base length = 2012=820 - 12 = 8
    • Area = rac{1}{2} (5.2 + 6.2) \times 8 = 44.8
  2. Trapezium 2: For the interval [20,30][20, 30]:

    • Height 1 = 6.26.2
    • Height 2 = 8.08.0
    • Base length = 3020=1030 - 20 = 10
    • Area = rac{1}{2} (6.2 + 8.0) \times 10 = 71.0
  3. Trapezium 3: For the interval [30,36][30, 36]:

    • Height 1 = 8.08.0
    • Height 2 = 6.06.0
    • Base length = 3630=636 - 30 = 6
    • Area = rac{1}{2} (8.0 + 6.0) \times 6 = 42.0
  4. Trapezium 4: For the interval [36,50][36, 50] is not included in this interval.

Thus, the total area can be summed up as: extTotalArea=44.8+71.0+42.0=157.8 m ext{Total Area} = 44.8 + 71.0 + 42.0 = 157.8 \text{ m}

Step 2

Compare the total area to Noosha's estimate

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Answer

Noosha estimated that the scooter travels approximately 130 metres during the time interval from 12t3612 \leq t \leq 36.

From our calculation, the total area under the curve is 157.8 m157.8 \text{ m}, which is greater than her estimate. Therefore, we conclude:

Noosha's estimate was not reasonable.

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