1. The problem statement, all variables and given/known data A particle of mass 1 gm starts from rest and moves under the action of a force of 30 Newtons defined in the rest frame. It will reach 99% the velocity of light in time (a) 9.9 x 10³ sec (b) 7 x 10⁴ sec (c) 0.999 sec (d) 0.7 sec 2. Relevant equations 3. The attempt at a solution I can safely disregard (c) and (d) (a) can be found by kinematic calculation.But as the particle moves in relativistic speed, this classical calculation does not hold. (b) looks correct to me. But how to prove this? Can anyone suggest anything?