Ball A of mass m, after sliding from an inclined plane, strikes elastically another ball B of same mass at rest. Find the minimum heihgt h so that ball B just completes the circular motion of the surface at C. (All surfaces are smooth).

Options

A. (a) `h=5/2R`
B. (b) `h=2R`
C. (c) `h=2/5R`
D. (d) `h=3R`

Answer

A

Explanation

`mgh=1/2mv^2+2mgR`
`gh=v^2/2+2gR`
Required velocity at the top, `v=sqrt(gR)`
`gh=(gR)/(2)+2gRimpliesh=5/2R`