When a particle is projected from the surface of earth its mechanical energy and angular momentum about center of earth at all time are constant.
Q. A particle of mass `m` is projected from the surface of earth with velocity `v_(0)` at angle 0 with horizontal suppose `h` be the maximum height of particle from surface of earth and v its speed at that point then v is`v_(0)cos0`

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`