A 2kg object has a position vector r = -4t i + 3t^2 j (m). Find its angular momentum relative to the origin as a function of time. The correct answer is -24t^2 k (kgm^2/s). I know that L = r*p and p is mv so I differentiate r to get v v = -4 i + 6t j do I just multiply 2 and the cross proudct of r and v? I don't know what to do because of the t in the equation for vector r.