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Simple Harmonic Motion question

2021 · 24 Feb · Shift 2 · Q51
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  5. /2021 · 24 Feb · Shift 2 · Q51

Simple Harmonic Motion question

2021 · 24 Feb · Shift 2 · Q51

JEE MainPhysicsSimple Harmonic MotionMCQ+4 / −1
The period of oscillation of a simple pendulum is T=2πLgT = 2\pi \sqrt {{L \over g}}T=2πgL​​. Measured value of 'L' is 1.0 m from meter scale having a minimum division of 1 mm and time of one complete oscillation is 1.95 s measured from stopwatch of 0.01 s resolution. The percentage error in the determination of 'g' will be :
  1. A
    1.30%
  2. B
    1.33%
  3. C
    1.13%
  4. D
    1.03%
View written solutionFree

Correct answer: C

  1. Relation for ggg

Given T=2πLgT = 2\pi\sqrt{\frac{L}{g}}T=2πgL​​

Squaring, T2=4π2LgT^2 = 4\pi^2\frac{L}{g}T2=4π2gL​

So, g=4π2LT2g = \frac{4\pi^2 L}{T^2}g=T24π2L​

  1. Error propagation

For g∝L T−2g \propto L\,T^{-2}g∝LT−2

The fractional error is Δgg=ΔLL+2ΔTT\frac{\Delta g}{g} = \frac{\Delta L}{L} + 2\frac{\Delta T}{T}gΔg​=LΔL​+2TΔT​

  1. Error in length measurement

Measured length: L=1.0 mL = 1.0\ \text{m}L=1.0 m

Minimum division of meter scale: 1 mm=0.001 m1\ \text{mm} = 0.001\ \text{m}1 mm=0.001 m

So, ΔL=0.001 m\Delta L = 0.001\ \text{m}ΔL=0.001 m

Hence, ΔLL=0.0011.0=0.001=0.1%\frac{\Delta L}{L} = \frac{0.001}{1.0} = 0.001 = 0.1\%LΔL​=1.00.001​=0.001=0.1%

  1. Error in time measurement

Measured time period: T=1.95 sT = 1.95\ \text{s}T=1.95 s

Stopwatch resolution: ΔT=0.01 s\Delta T = 0.01\ \text{s}ΔT=0.01 s

Thus, ΔTT=0.011.95≈0.005128\frac{\Delta T}{T} = \frac{0.01}{1.95} \approx 0.005128TΔT​=1.950.01​≈0.005128

So, 2ΔTT≈2(0.005128)=0.010256=1.0256%2\frac{\Delta T}{T} \approx 2(0.005128) = 0.010256 = 1.0256\%2TΔT​≈2(0.005128)=0.010256=1.0256%

  1. Total percentage error in ggg

Δgg=0.001+0.010256=0.011256\frac{\Delta g}{g} = 0.001 + 0.010256 = 0.011256gΔg​=0.001+0.010256=0.011256

In percentage, 0.011256×100≈1.13%0.011256 \times 100 \approx 1.13\%0.011256×100≈1.13%

  1. Option check

The percentage error is closest to: 1.13%\boxed{1.13\%}1.13%​

So the correct option is C.

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