A block is released from rest at the top of an inclined plane which later curves into a circular track of radius `r` as shown in figure. Find the minimum height `h` from where it should be released so that it is able to complete the circle.

Explanation

To complete the circle of radius `r`, the velocity at the top must be
`gesqrt(rg)`.
From A to B,
loss in GPE=Gain in `KEmg(h-2r)`
`=1/2mv^2=0`
`mg(h-2r)1/2m(sqrt(rg))^2impliesh=5/2r`

Hence, h must be at least equal to `2.5r`.