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JEE Mains · Physics · STD 11 - 13. oscillations

A person of mass \(M\) is, sitting on a swing of length \(L\) and swinging with an angular amplitude \(\theta_0\). If the person stands up when the swing passes through its lowest point, the work done by him, assuming that his centre of mass moves by a distance \(l\, ( l < < L)\), is close to

  1. A \(Mgl\,\left( {1 + \theta _0^2} \right)\)
  2. B \(Mgl\,\left( {1 - \theta _0^2} \right)\)
  3. C \(Mgl\)
  4. D \(Mgl\,\left( {1 + \frac{{\theta _0^2}}{2}} \right)\)
Verified Solution

Answer & Solution

Correct Answer

(A) \(Mgl\,\left( {1 + \theta _0^2} \right)\)

Step-by-step Solution

Detailed explanation

Angular momentum conservation \(\mathrm{MV}_{0} \mathrm{L}=\mathrm{MV}_{1}(\mathrm{L}-\ell)\) \(V_{1}=V_{0}\left(\frac{L}{L-\ell}\right)\) \(\mathrm{w}_{\mathrm{g}}+\mathrm{w}_{\mathrm{p}}=\Delta \mathrm{KE}\) \(-m g \ell+w_{p}=\frac{1}{2} m\left(V_{1}^{2}-V_{0}^{2}\right)\)…
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