Question

Ans the attachement​

Answer 1

Answer:

Hey!

Let total energy is conserved,

Total mechanical energy at start = Total mechanical energy at 'B'

mgh = 21 mv B2 +mgD ...........(1)

Minimum speed required to complete rotation is, vb = rr = Dg/2

Hence equation (1) becomes,

mgh = 21 m2Dg + mgD

hence, h= 45D

hope it will be helpful ✌️