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A uniform metal chain of mass \mathrm{m} and length \mathrm{ ' L '} passes over a massless and frictionless pulley. It is released from rest with a part of its length l is hanging on one side and rest of its length L-l is hanging on the other side of the pully. At a certain point of time, when {l=\frac{L}{x}}, the acceleration of the chain is \mathrm{\frac{g}{2}}. The value of \mathrm{x} is________________.

 

Option: 1

6


Option: 2

2


Option: 3

1.5


Option: 4

4


Answers (1)

best_answer

Let the mass of complete chain be \mathrm{' m ' }and mass of chain of length \mathrm{ ' \ell '} and \mathrm{ ' L-\ell '} be \mathrm{m_1 \: and \: m_2} respectively

\mathrm{m_1+m_2=m }

\mathrm{m_1=\left(\frac{m}{L}\right) \ell}

\mathrm{m_2=\left(\frac{m}{L}\right)(L-\ell) }

\mathrm{\left(m_2-m_1\right)_{g}=\left(m_2+m_1\right) a }

\mathrm{a=\left(\frac{m_2-m_1}{m_2+m_1}\right) g }

\mathrm{\frac{g}{2}=\frac{\left ( \frac{m}{L} \right )\left ( L-2\ell \right )}{m}g}

\mathrm{\frac{1}{2}=\frac{L-2\ell}{L}}

\mathrm{L=2L-4\ell}

\mathrm{4\ell=L}

\mathrm{\ell=\frac{L}{4}}

\mathrm{\therefore x=4}

Hence 4 is the correct option

Posted by

avinash.dongre

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