vel. at highest point = Vo/2

 

so applying energy of conservetion at instance , when it was at highest point & when its velocity is vertical(i.e at R(radius) distance above the lowermost point)

 

1/2 m . Vo^2/4 + 2mgR = 1/2 m v^2 + mgR.  ,where v is velocity at 2nd instance

 

from above we get

 

v^2 = Vo^2/4 + 2gR

 

now putting in eqn. we get

 

Vo^2/4 + 2gR = Vo^2 - 2aoR        ao = Ao

from above we get

 

Vo^2/R = radial accn. = 8(g - ao)/3