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A bob of mass m , suspended by a string of length l1 is given a minimum velocity required to complete a full circle in the vertical plane. At the highest point, it collides elastically with another bob of mass m suspended by a string of length l2, which is initially at rest. Both the strings are mass-less and inextensible. If the second bob, after collision acquires the minimum speed required to complete a full circle in the vertical plane, the ratio l1/l2 is |
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Answer» The initial speed of 1st bob (suspended by a string of length l1)is \(\sqrt{5gl_1}\). The speed of this bob at highest point will be \(\sqrt{gl_1}.\) When this bob collides with the other bob there speeds will be interchanged. \(\sqrt{gl_1}=\sqrt{5gl_2}\) ⇒ \(\frac{l_1}{l_2}\) = 5 |
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