Base unit (measurement) aspects of the world, such as time, distance, velocity, mass, temperature, energy, and weight, and "units" are used to describe their magnitude or quantity. Many of these quantities are related to each other by various physical laws, and as a result the units of a quantities can be generally be expressed as a product of powers of other units; for example, momentum is mass multiplied by velocity, while velocity is measured in distance divided by time. These relationships are discussed in dimensional analysis. Those that can be expressed in this fashion in terms of the base units are called .
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