In a large hadron collider at CERN, protos follow a circular path with speeds close to the speed of light. X-rays can be produced by free protons which are accelerating. Explain why this providesa source of x-rays even though the speeds of the protons are constant. Provided answer: must be accelerating due to circular motion (1) (Speed constant but) direction/velocity changing (1) I'm having trouble understanding how the answer relates to the question. It seems to be indicating that the instantaneous velocity or speed of the proton(s) stays the same but is still accelerating due to circular motion. However I don't see how this explains the 'source' of x-rays.