1. The problem statement, all variables and given/known data A 0.5-kg particle is located at the point r = 3m i + 4m k and is moving with a velocity v = 5m/s i -2m/s k . What is the angular momentum of this particle about the origin? A) 13 kgm^2/s k B) 13 kgm^2/s j C) 26 kgm^2/s k D) 26m^2/s j E) 13 kgm^2/s i 2. Relevant equations L = RxP where L is angular momentum, R is the distance from the origin and P is the momentum and the x stands for the cross product P = mv 3. The attempt at a solution P = 0.5(5m/s i - 2m/s k) = 5/2 kgm^2/s i - 1kgm^2/s L = (3i + 4i) x (5/2 kgm^2/s i - 1kgm^2/s) = -3j - 10j = -13j I'm fairly certain that the answer is B because I believe that the cross product should give me a value that is perpendicular to the two vectors, which in this case are i and k, thus the cross product should, I think, include j. Also, I believe that I can eliminate D because the units are incorrect. What I don't understand is why my answer is negative.