Chapter 39, Problem 39.2P

In a laboratory frame of reference, an observer notes that Newton’s second law is valid. Assume forces and masses are measured to be the same in any reference frame for speeds small compared with the speed of light. (a) Show that Newton’s second law is also valid for an observer moving at a constant speed, small compared with the speed of light, relative to the laboratory frame. (b) Show that Newton’s second law is not valid in a reference frame moving past the laboratory frame with a constant acceleration.