In finding b part can't we write the velocity of the particle farthest away from the point of suspension as it goes through its mean position as aw

Please respond to my asked ques not just providing the solution simply

Dear Student
This compound pendulum situation.
You can definitely write aw for velocity in b part.
But then you need to find value of a that is amplitude which will be 2rθ

So v = 2rθ​​​​​​​ w
w can be written as 2π/T

So
v = (2rθ) (2π/T)

​​​​​​​Regards