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 centre. At a certain instant of time, the stone is at its lowest position and has a speed 'u'. The magnitude of the change in velocity as it reaches a position where the string is horizontal $$($$ g being acceleration due to $$gravity)$$ is

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Infinity Learn · Accepted Answer

Applying the law of conservation of energy at points B and A, we $$have12mu2=12mv2+mglor$$      $$V=u2$$â$$2gl$$        â¦(1)This$$ magnitude of change of velocity figure is given by |Îv|$$=$$|vâu|$$=v2+u2$$â$$2uvcos$$â¡$$90$$â$$=v2+u2$$       ....$$(2)From$$ eqs, $$(1) and (2), we get|Îv|$$=u2$$â$$2gl+u2=2u2$$âgl

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