NECO 2002 Mathematics · Question 20

If tL\frac{t}{L} = (4π2g)\sqrt{(\frac{4\pi^2}{g}}), what is the value of g when L = 4.5; t = 5 secs

Options

  1. A.3.20 ms2
  2. B.11.31 ms2
  3. C.32.00 ms2
  4. D.56.57 ms2
  5. E.160.00 ms2

Answer: C. 32.00 ms2

Explanation written with AI and checked against the answer key

Analyze the question: We are given t/L = √(4π²/g) and need g when L = 4.5 and t = 5. The plan is to make g the subject of the formula, then substitute.

Concept: To remove a square root, square both sides. Then rearrange to isolate g.

Step 1: Square both sides

(t/L)² = 4π²/g

Step 2: Make g the subject

g = 4π² · (L/t)² = 4π²L²/t²

Step 3: Substitute the values (π ≈ 3.142, so 4π² ≈ 39.478)

  • L² = (4.5)² = 20.25
  • t² = 5² = 25

g = 39.478 × (20.25 / 25) g = 39.478 × 0.81 g ≈ 31.98 ≈ 32.00 m/s²

Answer: Option C, 32.00 m/s².

Tip: When a formula has a square root, square both sides first. Then rearrange to isolate the unknown. Using π ≈ 3.14 gives about 31.9, which is still closest to 32.00, so the options are well separated.

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