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NEET 2004
Exam
NEET
Year
2004
Subject
Physics
Chapter
Work, Power and Energy

NEET 2004 · Physics · Work, Power and Energy

A stone is tied to a string of length ' l ' and is whirled in a...

A stone is tied to a string of length ' ll ' and is whirled in a vertical circle with the other end of the string as the centre. At a certain instant of time, the stone is at its lowest position and has a speed ' uu '. The magnitude of change in velocity as it reaches a position where the string is horizontal ( gg being acceleration due to gravity)is:A stone is tied to a string of length ' l ' and is whirled in a vertical circle with the other end of the string as the

Options

  1. A\sqrt{2\left(u^2-g l\right)}
  2. Bu2−gl\sqrt{u^2-g l}
  3. Cu−u2−2glu-\sqrt{u^2-2 g l}
  4. D2gl\sqrt{2 g l}

Correct answer

A. \sqrt{2\left(u^2-g l\right)}

Step-by-step solution

According to the question Total energy at A=\mathrm{A}= Total energy at B\mathrm{B} A stone is tied to a string of length ' l ' and is whirled in a vertical circle with the other end of the string as the ⇒12mu2=12mv2+mgl⇒v2=u2−2gl\begin{array}{l} \Rightarrow \frac{1}{2} m u^2 =\frac{1}{2} m v^2+m g l \\ \Rightarrow v^2 =\sqrt{u^2-2 g l} \end{array} ∴\therefore Change in magnitude of velocity =\sqrt{u^2+v^2}=\sqrt{2\left(u^2-g l\right)}
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