the physics factor

Quantum Physics

Reduced mass μ

Reduced mass μ is used throughout physics and engineering as a correction ‘factor’ for interacting particles whose interaction affects the centre of mass. It is given by

where m is the mass of the particle and M is the mass of the particle it interacts with. For example, the reduced mass μe of an orbital electron is given by

where me is the mass of the orbiting electron and mp is the mass of the proton. This is due to their mutual interaction given by Newton’s Third Law of Motion, which causes the two to rotate about a mutual origin of orbit, instead of at the centre of mass of either one of the particles.

Multiple bodies

The reduced mass mN of N mutually interacting bodies is given by

where mn is the mass of the nth body.

Relativistic correction

See posts about special relativity.

The reduced mass often sees an additional relativistic correction, given for N bodies by

since mrel = γm for a rest mass m. Note that γn is the Lorentz factor for the nth body travelling at velocity vnc, defined such that

For only two bodies, this simply becomes

Why is it that if you take advantage of a tax break and you’re a corporation, you’re a smart business man. But if you take advantage of something you need to not be hungry, you’re a moocher!
—  Jon Stewart, O’Reilly vs. Stewart

First Order LDE and that mysterious Integrating Factor.

The integrating factor can be deeply confusing if you don’t understand what it does. This was an attempt to explain the first order linear differential equation to a friend. 

(Sorry about the image quality though. I had to make these in a hurry )

TIPS: Choosing a Career

NOTE: Take into account that this is my simple opinion and the things that I did to decide my professional course. The following points are only tips.

  •  Vocational tests are quite common, and I indicate the ones with a psychologist (if not possible, the person can be an adviser / manager / school principal or a teacher of confidence, even if only to talk about it). Online tests (like everything on the Internet) are not the best.
  •  Eliminate what it’s NOT. Start seeing which area (humans, exacts, biologicals) you are better and / or more interested in and take off what you know is not for you, For example, when I started thinking about medicine, I knew from the start that any kind of engineering would be discarded (can not stand mathematics and physics). Another important factor during this process is to know enough about the areas that interest you, which brings us to the next point:
  •  Research. There is no way to decide a profession with only what you know or heard about. Reseach about the profession and the course itself. Imagine if you decide for psychology because you find it interesting, but later you realize it’s not like you thought it would be? Or maybe you chose architecture and realize that you had more affinity with civil engineering? Acquiring information is essential at this time. Also, speak to professionals, they know better than any website.
  •  Consider your ability, as well as personal satisfaction. Many people opt for “big” careers  (med, law, eng …) because of the money or the status that they will provide. Note that is (possibly) what you choose to do for a long time, if not the rest of his professional life. You need LIKE what you do. Again, I stress the importance of counseling and / or vocation tests.
  •  Remember, It doesn’t have to be a final decision.
  • Finally, look at the pros and cons of the profession. Ask yourself: “Is it worth it?” “Could I do that?” If the answer is “yes”, then you already have something to be considered.

anonymous asked:

heeeeyyyy! I'm a freshman at uni taking B.S. Physics. Have any advice for me? (and for others who also dream of getting their own PhD in the field) p.s. i love your yt channel p.p.s oHMYGOD YOU LOVE LEGEND OF KORRA I LOVE YOU p.p.p.s. YOU'RE AWESOME

Hi anon!

Sometimes I wish tumblr timestamped these things because I have no idea when you wrote this, but hopefully not too long ago…(I took quite a break from the internet over the holidays).


(1) You are studying physics AND you are a Legend of Korra fan??? I LOVE YOU BACK (there must be something especially appealing to physicists about Korra…@PhysicistLisa is also a huge fan!)

(2) The best thing you can do to get yourself well on the road to a PhD is to get involved in research early on in college. (I would say the summer after your freshman year, if possible; just use freshman year to adjust to college life and set good habits to do well in your classes.) It can definitely be challenging to get involved in research so early, because you won’t have as huge a physics knowledge base as older students. But don’t let this discourage you: ask around and find out which professors take a lot of undergrads. You would almost certainly be working an experimental job, helping prepare samples and perhaps building things, since you’d likely be underprepared for theory work. I can think of professors at both UCSB and Cornell who have a reputation for taking on undergrads, so hopefully you can find someone similar at your uni! If not, that’s ok, just keep at it - many students are able to find positions after sophomore year.

(3) Thank you so much for your note! :D I’m trying to figure out how to manage my channel this year, since I didn’t do a great job of it last year…research, man! So thank you for your encouraging words - they mean a lot and are hugely motivating. :)