I have a question please that I need help on.

Consider the chain that is draped over the sprocket with mass moment of inertia of 0.005kgm^2 about central axis. If 4kg block is released from rest from H=1, by using energy approach what is angular velocity of sprocket at H=2? Radius of sprocket is 100mm. Where H is from sprocket to mass.

Help please

I tried using WyG=1/2Igw^2+ 1/2mv^2 and got 41.76rad/s. Though, I spoke to my teacher and he said it is slightly off? But I don’t see what I did wrong? I posted another questions as the other one is closed