Center of mass rigid body, the gravity forces will not cause the body to rotate, which means the weight of the body can be considered to be concentrated at the center of mass. The linear and angular momentum of a collection of particles can be simplified by measuring the position and velocity of the particles relative to the center of mass. Let the system of particles "P", "i"=1...,"n" of masses "m" be located at the coordinates r with velocities v. Select a reference point R and compute the relative position and velocity vectors, The total linear and angular momentum vectors relative to the
Cross product formula_123 is its velocity and formula_124 is the body's angular velocity. Since position formula_110 and velocity formula_123 are "true" vectors, the angular velocity formula_124 is a "pseudovector" or "axial vector". The cross product is used to describe the Lorentz force experienced by a moving electric charge formula_128: Since velocity formula_123, force formula_118 and electric field formula_132 are all "true" vectors, the magnetic field formula_133 is a "pseudovector". In vector calculus, the cross product is used to define the formula for the vector operator curl. The trick of rewriting a cross product in terms of a matrix multiplication appears frequently in