When a particle is projected from the surface of earth, its mechanical energy and angular momentum about centre of earth at all time is constant .
A particle mass m is projected from the surface of earth with velocity `v_(0)` at angle `theta` with horizontal. Suppose h be the maximum height of particle from surface of earth and v its speed at that point then v is

Options

A. `gtv_(0)costheta`
B. `ltv_(0)costheta`
C. zero
D. `lt(v_(0)^(2)sin^(2)theta)/(2g)`

Answer

B

Explanation

By applying conservation of angular momentum
`mv_(0)Rcostheta=mv(R+h)`
`v=(v_(0)Rcostheta)/(R+h)((R)/(R+h)lt1)impliesv_(0)costhetagtv`