A projectile of mass m fired with velocity u making angle θ with the horizontal, its angular momentum about the point of projection when it hits the ground is given by
(a) (2mu sin2θ cosθ) / g
(b) -(2mu3 sin2θ cosθ) / g
(c) (mu sin2θ cosθ) / g
(d) (mu3 sin2θ cosθ) / g
Answer is (b) -(2mu3 sin2θ cosθ) / g
L = vector(r x p) = vector(R x P) where R = range = (u2 sin 2θ)/g.
the angle between vector(R & p) is = θ. Also p = mu.
Hence L = [(u2 sin2θ) / g] x mu sin (-θ) = -(2mu3 sin2 θ cos θ] / g .