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2 (a) Rearrange this formula to make u the subject - OCR - GCSE Maths - Question 2 - 2023 - Paper 6

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2 (a) Rearrange this formula to make u the subject. $$v^2 = u^2 + 2as$$ (b) A rocket accelerates at 90 m/s² and travels 270 km. The rocket's final velocit... show full transcript

Worked Solution & Example Answer:2 (a) Rearrange this formula to make u the subject - OCR - GCSE Maths - Question 2 - 2023 - Paper 6

Step 1

Rearrange this formula to make u the subject

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Answer

To rearrange the formula v2=u2+2asv^2 = u^2 + 2as to make u the subject, we start by isolating u2u^2 on one side:

  1. Subtract 2as2as from both sides: v22as=u2v^2 - 2as = u^2

  2. Take the square root of both sides: u=ext±sqrtv22asu = ext{±} \\sqrt{v^2 - 2as} This expression gives us the value of u.

Step 2

Using part (a), or otherwise, calculate the rocket's initial velocity

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Answer

From part (a), we have the formula: u=ext±sqrtv22asu = ext{±} \\sqrt{v^2 - 2as}

Given:

  • Final velocity v=8000m/sv = 8000 \, m/s
  • Acceleration a=90m/s2a = 90 \, m/s^2
  • Distance s=270km=270000ms = 270 \, km = 270000 \, m

Now, substituting the values into the equation:

  1. Calculate 2as2as: 2imes90imes270000=486000002 imes 90 imes 270000 = 48600000

  2. Now substituting in the rearranged formula: u=ext±sqrt8000248600000u = ext{±} \\sqrt{8000^2 - 48600000} =ext±sqrt6400000048600000= ext{±} \\sqrt{64000000 - 48600000} =ext±sqrt15400000= ext{±} \\sqrt{15400000} 3932.0m/s≈ 3932.0 \, m/s

Since initial velocity cannot be negative, we choose the positive value: u3932.0m/su ≈ 3932.0 \, m/s

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