The relativistic mass of an object refers to the measured mass of an object moving relative to the observer. A moving object appears to have a larger mass than the same object at rest. The mass of the object is directly related to its total energy...

The term mass in special relativity is commonly used by physicists to mean a quantity that does not depend on the observer or the inertial frame used to observe it. However, because the term relativistic mass is also used, this occasionally leads to...