ltbgt Find the velocity of block B when ring A is moving downward with velocity v.

Explanation

`L=sqrt(x^(2)+h^(2))+y=` constant
`(dL)/(dt)=(1)/(2)(x^(2)+h^(2))^(-1//2)(0+2h(dh)/(dt))+(dy)/(dt)`
`(dL)/(dt)=0,(dh)/(dt)=v,(dy)/(dt)=-v_(B)`
`0=(h)/(sqrt(x^(2)+h^(2)))v-v_(B)impliesv_(B)=vcostheta`
OR
`v_(B)=vcostheta`