A body is moving according to the equation `x=at+bt^(2)-ct^(3)`. Then its instantaneous speed is given By :-

Answer

B

Explanation

At maximum height vertical component of velocity becomes zero.
`v^(2)=u^(2)+2as`

For A : `0=v_(A)^(2)sin^(2)60^(@)-2gh`
`2gh=v_(A)^(2)sin^(2)60^(@)=v_(A)^(2)(3//4)`
`v_(A)=sqrt((8gh)/3)`
For B : `0=v_(B)^(2)-2gh`
`v_(B)=sqrt(2gh), v_(A)/v_(B)=2/sqrt(3)`