A block slides down a smooth inclined plane when released from the top, while another falls freely from the same point :

Explanation

In case of sliding motion on an inclined plane.
`(h)/(s)=sin theta rArr s=(h)/(sin theta), a=g sin theta`
`t_(s)=sqrt((2s)/(a))=sqrt((2)/(g sin theta)xx(h)/(sin theta))=(1)/(sin theta)sqrt((2h)/(g))=(t_(F))/(sin theta)`
`v_(s)=sqrt(2as)=sqrt(2g sin thetaxx(h)/(sin theta))=sqrt(2gh)=v_(F)`
In case of free fall `t_(F)=sqrt((2h)/(h))` and `v_(F)=sqrt(2gh) v_(s)=v_(P)`
(a) `because sin thetalt1,t_(F)ltt_(s),i.e.` falling body reaches the ground first.
(b) `v_(F)=v_(s), i.e.,` both reach the ground-with same speed