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JEE Mains · Physics · STD 11 - Work,energy,power and collision
  • JEE Mains 2026
  • Medium
  • MCQ

In case of vertical circular motion of a particle by a thread of length \(r\) if the tension in the thread is zero at an angle \(30^{\circ}\) shown in figure, the velocity at the bottom point (A) of the circular path is ( \(g =\) gravitational acceleration)
image

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Answer & Solution

Correct Answer

(B) \(\sqrt{\frac{7}{2}gr}\)

Step-by-step Solution

Detailed explanation


image
\(T + mg \cos 60^{\circ}=\frac{ mV ^2}{\ell}\)
\(T =0\)
\(V ^2=\frac{ g \ell}{2}\) here V is the speed at point A
M.E.C.
\(\frac{1}{2} mu ^2= mg \left(\ell+\ell \cos 60^{\circ}\right)+\frac{1}{2} mV ^2\)
\(u ^2=3 g \ell+\frac{ g \ell}{2}\)
\(u =\sqrt{\frac{7 g \ell}{2}}\)
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