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A yo-yo consists of two discs mounted on an axle. A length of string is attached to the axle and wound round the axle.
With the string fully wound, the yo-yo is suspended from a horizontal support.
The yo-yo is released from rest and rotates as it falls.
The string is funny unwound at the yo-yo's lowest point.
The yo-yo then rises, rewinding the string.
© When the yo-yo is at its lowest point, it has an angular velocity of 120 rad/s.
Calculate the maximum height to which the yo-yo could rise as it rewinds the string.
(Data from other questions: mass=0.1kg, radius=0.05m, moment of inertia=2.5x10^-4)
With the string fully wound, the yo-yo is suspended from a horizontal support.
The yo-yo is released from rest and rotates as it falls.
The string is funny unwound at the yo-yo's lowest point.
The yo-yo then rises, rewinding the string.
© When the yo-yo is at its lowest point, it has an angular velocity of 120 rad/s.
Calculate the maximum height to which the yo-yo could rise as it rewinds the string.
(Data from other questions: mass=0.1kg, radius=0.05m, moment of inertia=2.5x10^-4)
I've tried two methods so far:
(1) Changing angular velocity to linear velocity, then using
(2) Ep = Rotational Ek
but both result in 1.84m, which is twice the value given in the answer booklet (0.92m. in case you can't divide by two
) If anyone can help, I will love you forever 
