The type of potential energy is elastic energy
There are six distinct changes of phase which happens to different substances at different temperatures. ... Sublimation: the substance changes directly from a solid to a gas without going through the liquid phase. Deposition: the substance changes directly from a gas to a solid without going through the liquid phase.
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Here since both children and merry go round is our system and there is no torque acting on this system
So we will use angular momentum conservation in this

now here we have



Now when children come to the position of half radius
then we will have



now from above equation we have

