Lesson: Relativistic Mass

Person A is sitting on a train that is moving at 80 km/h. Person B is standing next to the train tracks. The following formula can be used to calculate how much extra mass person A appears to have, as perceived by person B: extra mass .

If person A has a rest mass, , of 80 kg, how much extra mass are they perceived to have by person B? Give your answer to 3 significant figures (the answer will be very small, but not zero).

The graph shows relativistic mass, , against rest mass, , for objects moving at speed relative to an observer. What is the value of ? Give your answer as a multiple of .

What is the mass, as measured by an observer, of a metal sphere that has a rest mass of 2.00 kg and is moving at relative to the observer? Give your answer, in kilograms, to 3 significant figures.