Physics, angular motion

[Stavik]

The first image is the photo of the question.
I tried to solve the second part by using the kinamatic formula:
Vf^2 = vi^2 +2a∆X - And converted it into angular parameters.
And the solution on the site used another formula: vf = vi + 2at

I can’t understand why we got different answers, because I know that no matter what formula you use - the answer will be the same.
I’m sure I have a mistake, I just can’t see where…

[AriHoresh]

Hey guys @winter1 @Juliette ! I find it a bit difficult myself, is it something you are more familiar with? Thank you

[winter1]

My theory is that there is an error on the yellow circle.

I used the fact that Distance is (means of velocity) * time,

therefore 0.15s.

Hope it’s correct

[Stavik]

This is amazing, thank you! I needed the average angular velocity, not the final… Thanks for helping