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JEE Main 2026 (28 Jan, Shift 2) · Errors in Measurement

Errors in Measurement question from JEE Main 2026 (28 Jan, Shift 2)

Q35JEE Main 2026 · 28 JAN · SHIFT 2Difficult

Errors in Measurement

The time period of a simple harmonic oscillator is T=2πmkT = 2\pi\sqrt{\frac{m}{k}}. Measured value of mass (m)(m) of the object is 10 g with an accuracy of 10 mg and time for 50 oscillations of the spring is found to be 60 s using a watch of 2 s resolution. Percentage error in determination of spring constant (k)(k) is ________%.

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Answer: (d)

  1. T=2πm/k⇒k=4π2mT2T = 2\pi\sqrt{m/k} \Rightarrow k = \dfrac{4\pi^2 m}{T^2}, so Δkk=Δmm+2ΔTT\dfrac{\Delta k}{k} = \dfrac{\Delta m}{m} + 2\dfrac{\Delta T}{T}.
  2. Δmm=10 mg10 g=0.1%\dfrac{\Delta m}{m} = \dfrac{10\text{ mg}}{10\text{ g}} = 0.1\%
  3. ΔTT=Δtt=260=3.33%\dfrac{\Delta T}{T} = \dfrac{\Delta t}{t} = \dfrac{2}{60} = 3.33\%, so 2ΔTT=6.67%2\dfrac{\Delta T}{T} = 6.67\%
  4. Total ≈0.1%+6.67%≈6.76%\approx 0.1\% + 6.67\% \approx 6.76\%, answer (d).
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