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. H=3R
B. H=2R
C. `H=(5R)/2`
D. H=4R

Answer

C

Explanation

For the just completing the circular motion, minimum velocity at bottom in `V_(B)=sqrt(5gR)`
Energy conservation b/w point A and B
`MgH+0=0+1/2 mv_(B)^(2)`
`MgH =1/2 m (5gR)`