A particle is projected with a speed v  at 450  with the horizontal. The magnitude of angular momentum of the projectile about the point of projection when the particle is at its maximum height h , is:

Velocity of a particle at maximum height h  is v'=vcosθ Where v= initial velocity of the particle at which it is projected,θ=  angle of projectionAngular momentum, L=mv'h=mv cosθh =mvhcos450=mvh2