Work, Power and EnergyHard
Question
A stone tied to a string of length L is whirled in a vertical circle with the other end of the string at 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 its velocity as it reaches a position, where the string is horizontal, is
Options
A.

B.

C.

D.

Solution
From energy conservation v2 = u2 - 2gL ....(i)
Now, since the two velocity vector shown in figure are mutually perpendicular, hence the magnitude of change of velocity will be given by
Substituting value of v2 from Eq. (i)

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