In general relativity, light is subject to gravitational pull. Does light generate gravitational pull, and do two beams of light attract each other?

Many physics papers now have dozens of authors per paper. Experimental physics may have multi-organizational and multi-country contributing staffs, but I'd guess that most of the names don't contribute a word or equation to a paper, yet they get individual authorship credit. My question is who determines the author list, does everybody listed have editing privilages, and perhaps most importantly, who decides on their listed order?   

A particle moves in the x-y plane with constant acceleration. At time zero, the particle is at r = <5.0, 2.0> m and has velocity v = <-4.0, 9.0> m/s. The acceleration is constant and is given by a = <4.0, 6.0> m/s2 . (a) Find the velocity at t = 2.0 s. (b) Find the position at t = 4.0 s. Give the magnitude and direction of this position vector. (c) Sketch (approximately to scale) the vector diagrams for vi , vf , and ?v, and for ri , rf , and ?r

From the "no hair theorem" we know that black holes have only 3 characteristic external observables, mass, electric charge and angular momentum (except the possible exceptions in the higher dimensional theories). These make them very similar to elementary particles. One question naively comes to mind. Is it possible that elementary particles are ultimate nuggets of the final stages of black holes after emitting all the Hawking radiation it could?

What percentage of physics PhDs leave physics to become quantitative analysts, work in computer science/information technology or business? Is physics that bad that so many people leave? Was it worth it?

Will a CFL light bulb and an incandescent light bulb, in separate respective closed systems, produce exactly the same amount of overall temperature increase over time?

Assume you have two identical closed systems with gray walls, with a system input of 20 watts of power each.

EDIT added for clarity: (On the packaging of the CFL light bulb the large print equivalent wattage is irrelevant... the input current of both bulbs is a consistent 20 watts of power each. The comparison wattage vs. the actual wattage of the CFL is off subject.)

One has a CFL, one has an ordinary incandescent light bulb. Will both systems increase in heat the exact amount, every hour?

Due to conservation of energy it shouldn't matter if one light source is more efficient, right?... it's the same amount of energy input. One light makes more heat one makes more light, but the light when it hits the gray wall is converted to heat, right?

There is no such thing as loss of energy... it's just converted to another form of energy... and light is converted to heat, right?

The back story of this question is my wondering that if my wife leaves an incandescent light bulb on in the winter time it's not so bad because even though no one is in the room it's still heating up the room. On the other hand if she leaves on a CFL it's more efficient but it should still add heat to our "system," i.e., our home.

(a) Consider two identical metal plates of area A, separated by a non-conducting material which has a thickness d. They are connected in a circuit with a battery and a switch, as shown above. When the switch is open, there is no excess charge on either plate. The switch is then closed. What will happen to the amount of net excess charge on the metal plate that is attached to the negative terminal of the battery? What will happen to the amount of net excess charge on the plate that is connected to the positive terminal of the battery? Explain.

(b) Can excess charges on one plate of a charged parallel plate capacitor interact with excess charges on the other plate? If so how? Note: To say that two charges interact is to say that they exert forces on each other from a distance.

(c) Is there any limit to the amount of charge that can be put on a plate? Explain.

(d) Use qualitative reasoning to anticipate how the amount of charge a pair of parallel plate conductors can hold will change as the area of the plates increases. Explain your reasoning.

(e) Do you think that the amount of net excess charge a given battery can store on the plates will increase or decrease as the spacing, d, between the plates of the capacitor increases? Explain

An airplane flies 560 miles with a tailwind in 2 hours 20 minutes. It takes 3 hours to fly against the headwind. Find the speed of the airplane in still air and the speed of the wind.

A mountain climber stands at the top of a 50 m cliff that over hangs a calm pool of water. She throws two stones vertically downward 1.00 sec apart and observes that they cause a single splash. The first stone had an initail velocity of -2.00 m/s (a) how long after release of the first stone did the two stones hit the water? (b) what initail velocity must the second stone have had , given that they hit the water simultaneously? (c) what was the velocity of each stone at the instant it hit the water?

I admit, it's been a few years since I've studied physics, but the following question came to me when I was listening to a talk by Lawrence Krauss.

Is there any knowledge of from where matter that exists today originated? I recall that the law of conservation of mass asserts that matter cannot be created nor destroyed, but surely the matter we see today had to be created at some point? Perhaps I am applying this law in the wrong fashion.

The reason I ask, is because Krauss mentioned that the elements of organic matter where created in stars, not at the beginning of time (whenever that may have been), but I ask, where did the building blocks for these elements arise? Were they too created in stars? If so, from where did their constituent building blocks come?

Please forgive me if this off topic, it is my first post on this particular stackexchange site. Thank you.

If naturally occurring ⁴⁰K is responsible for a dose equivalent of 0.16 mSv/y of background radiation, calculate the mass of ⁴⁰K that must be inside the 59 kg body of a woman to produce this dose. Assume that each ⁴⁰K decay emits a 1.30 MeV β, and that 40% of this energy is absorbed inside the body. The half life of ⁴⁰K is 1.25 × 10⁹ years.
_______ g

(a) Compute the derivative of the speed of sound in air with respect to the absolute temperature, and show that the differentials dv and dT obey dv/v=1/2 dT/T. (b) Use this result to estimate the percentage change in the speed of sound when the temperature changes from 0

I want to create a stream of water that emits only a droplet of water, waits a few milliseconds, and then continues. The important thing is that I need to create a visible gap between drops.

Considering the desire to have droplets created with a consistent size and shape (asked in this question), how would one go about creating a stream analogous to a morose-code-stream of droplets?

[Edit]

I'm considering having a solenoid valve connected to a tube pointed downward, where capillary action holds the water in place. The solenoid releases the amount equal to one droplet of water. What I'm having trouble with is making the drops look semi-uniform as they fall.

Here is an artistic rendering of what I'm trying to accomplish:

Clearly there will be differences like air resistance; I'm not interested in that. It seems like you're working against gravity when you're actually running in a way that you're not if you're on a treadmill, but on the other hand it seems like one should be able to take a piece of the treadmill's belt as an inertial reference point. What's going on here?

Although I doubt somewhat whether this question is really appropriate for this site, I hope it gets answered anyways. I guess, what I'm wondering is:

1. How does one get to work as a theoretical physicist and - probably more importantly - what do theoretical physicist actually do all day long?

2. How are theoretical physicists distinguishable from mathematicians? Does a physicists day look very different from that of a mathematician?

3. I have a great interest in physics, but I'm not really much interested in doing experiments: Would it be advisable to do my bachelor in mathematics and try to get into theoretical physics later on?

4. Is there a real chance of getting into research afterwards? (not that any kind of answer to this question would ever stop me from trying...)

Well, I hope this question is acceptable.

I think 1) might for example be answered by giving a link to a blog of a working theoretical physicist, who gives some insight into his or her everyday life, or some kind of an essay on the topic. Of course any other kind of answer is greatly appreciated.

Thanks in advance!

Kind regards