A ball at rest is dropped from a height of 12 m. It losses 25% of its kinetic energy on striking the ground and bounces back to a height 'h'. then value of 'h' is

Options

A. 3m
B. 6m
C. 9m
D. 12m

Answer

c

Explanation

Energy when at rest,P.`E_(1)=mgh `
`p.E_(2)=mgh_(2)`
percentage loss in `KE=(P.E_(1)-P.E_(2))/(P.E_(1))xx100`
i.e,` 25/100=(12-h_(2))/12`
`h_(2)=-[(25xx12/100-12)/100-12] `
`h_(2)=9m `