Explanation:
From conservation of mechanical energy
\(K.{E_B} = P.{E_A} - P.{E_B}\)
\(\frac{1}{2}m{v^2} = mgh - mg2r = mg(h - 2r)\)
\({v^2} = 2g(h - 2r)\,\,\,\,\,\,\,\,\,\,\,\,(1)\)
Given that
\(\frac{{m{v^2}}}{r} = xmg + mg\)
\( \Rightarrow {v^2} = (x + 1)rg\,\,\,\,\,\,(2)\)
From Eqs (1) and (2), we get
\(2 g(h-2 r)=(x+1) g r\)
or \(2 g h=(x+1) g r+4 g r=(x+5) g r\)
\(h=\left(\dfrac{x+5}{2}\right) r\)