**Unformatted text preview: **variable mass it’s force = rate of change of momentum, and if the mass changes the momentum changes, even at constant velocity. An instructive extreme case is the kinetic energy of a particle traveling close to the speed of light, as particles do in accelerators. In this regime, the change of speed with increasing momentum is negligible! Instead, where as usual c is the speed of light. This is what happens in a particle accelerator for a charged particle in a constant electric field, with F = qE . Since the particle is moving at a speed very close to c , in time dt it will move cdt and the force will do work Fcdt . The equation above can be rewritten So the energy dE expended by the accelerating force in the time dt yields an increase in mass, and Provided the speed is close to c , this can of course be integrated to an excellent approximation, to relate a finite particle mass change to the energy expended in accelerating it....

View
Full Document