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JEE Main 2021 (1 Sep, Shift 2) · Spring Systems

Spring Systems question from JEE Main 2021 (1 Sep, Shift 2)

Q68JEE Main 2021 · 1 SEP · SHIFT 2Medium

Spring Systems

A mass of 5 kg is connected to a spring. The potential energy curve of the simple harmonic motion executed by the system is shown in the figure. A simple pendulum of length 4 m has the same period of oscillation as the spring system. What is the value of acceleration due to gravity on the planet where these experiments are performed?

Figure

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Answer: (c)

  1. From the graph, equilibrium at x=2x = 2 m and U=10U = 10 J at the turning points, so A=2A = 2 m.
  2. 12kA2=10⇒12k(2)2=10⇒k=5 N/m\frac{1}{2}kA^2 = 10 \Rightarrow \frac{1}{2}k(2)^2 = 10 \Rightarrow k = 5\text{ N/m}
  3. T=2πmk=2π55=2π sT = 2\pi\sqrt{\frac{m}{k}} = 2\pi\sqrt{\frac{5}{5}} = 2\pi\text{ s}
  4. Pendulum: 2π4g=2π⇒g=4 m/s22\pi\sqrt{\frac{4}{g}} = 2\pi \Rightarrow g = 4\text{ m/s}^2
  5. So the answer is (c) 4 m/s2^2.
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