Q: A particle of mass m is moving in yz-plane with a uniform velocity v with its trajectory running parallel to +ve y-axis and intersection z-axis at z = a in figure. The change in its angular momentum about the origin as it bounces elastically from a wall at y = constant is
(a) m v a e ̂_x
(b) 2mvae ̂_x
(c) ymve ̂_x
(d) 2 ymve ̂_x
Ans: (b)