Newton's third law **
In the laboratory frame, a proton is at rest at the origin at t=0. At that instant a negative pion (charge −e) that has been traveling in along the x axis at a speed of 0.6c reaches the point x=0.01 cm. There are no other charges around. What is the magnitude of the force on the pion? What is the magnitude of the force on the proton? What about Newton's third law? (We're getting a little ahead of ourselves with this last question, but see if you can answer it anyway.)