Hey I take ap chemistry in my school. Electroweaks exactly a form of matter like atoms and crap. Its really a force (in theory) consisted of electromagnetism and some kind of "weak forces" if I recall correctly (whatever that is). Basically you can kinda compare to gravity. Its a force we know exist but does not take up space or mass (meaning its not a form of matter). So if your weighing the traveler there's no need to input electroweaks into your equations.(since its not a form of matter I don't think that would even be possible!). As long as your work is consistent with what you are sure the traveler is made of (like lead) you should be fine. Also make sure you take the scratches on the traveler into account :)