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location London, United Kingdom
age 29
visits member for 3 years, 2 months
seen Dec 3 '12 at 15:05

Phd student


May
18
comment physics- momentum ( a space question)
A little nitpicky perhaps but using the same $m$ for mass and meters could be a little confusing.
May
18
asked Famous physicists' quotations
May
18
comment Is anti-matter matter going backwards in time?
Great answer. +1
May
18
comment physics- momentum ( a space question)
Hint: 1st: velocity $ v=d/t $, substitute in distance and time to find the required velocity. 2nd: momentum is conserved. $ p=mv $ for both the astronaut and the spanner, equate them. Rearrange to solve. All the best ;)
May
17
awarded  Critic
May
17
comment How is a magnetic field translated into physical force?
@Justicle - to quote Feynman from 3min58 in the aforementioned video: "when you ask, for example, why two magnets repel - there are many different levels, it depends on whether you're a student of physics or an ordinary person who doesn't know anything." I therefore have two points to make to qualify my previous comment: 1/ To quote the FAQ for this site "Physics - Stack Exchange is for active researchers, academics and students." and 2/ you asked a 'how' question and not a 'why'. That said, if you're happy with this hand-wavey style of answer then I'll happily let sleeping dogs lie..
May
16
comment How is a magnetic field translated into physical force?
@Lubosh, lol, unfortunately not. Funnily enough, I came across that Feynman quote again yesterday, whilst re-watching Sidney Coleman's QMIYF. Actually I think an answer here is possible given that the OP didn't say "without reference to Maxwell's equations or vector calculus". My point was, I'm confident that it should be possible to illustrate how the force on the table-bound magnet is manifest from the change in flux density of the B-field, caused by the approach of the other magnet. Unfortunately my EM lecturer was pants so, personally, I don't feel confident enough to post a concise answer
May
16
comment How is a magnetic field translated into physical force?
Strange that you've neglected any mention of how the force is transmitted by the B-field. I'm pretty sure this was what the OP asked, unless I've missed the mark ;)
May
15
comment Video documentaries about physics?
A couple more good BBC ones include: Prof. Brian Cox's 'Wonders of the Solar System' followed by series two 'Wonders on the Universe'. Also search for a 2-part documentary by Prof. Jim Al-Khalili called 'Everything and Nothing'.
May
14
comment Feedback on the paper, 'CCC-predicted low-variance circles in CMB sky and LCDM' by V. G. Gurzadyan and R. Penrose
I'll gladly give you an actual +1. A highly impressive and convincing tirade.
May
14
accepted Is there a fully quantum-field theoretic treatise of Planck's Law for black-body radiation?
May
14
accepted Is it pions or gluons that mediate the strong force between nucleons?
May
14
accepted On black holes, Hawking radiation and gravitational atoms
May
13
comment Tension in a curved charged wire (electrostatic force) - does wire thickness matter?
A very interesting question.. +1
May
13
comment Does the Planck scale imply that spacetime is discrete?
Another related: physics.stackexchange.com/q/4453
May
13
comment Is it pions or gluons that mediate the strong force between nucleons?
@Lubosh, belay that last request, I just found a 12page study into whether or not the pion model is appropriate to teach at a pre-University level. For anyone interested it's here: teachers.web.cern.ch/teachers/archiv/HST2002/feynman/…
May
13
comment How do you explain spinning tops to a nine year old?
+1 for the bicycle wheel suggestion. It's a great way to get the point across in a way that can really be seen, and felt. Careful not to catch your nose on the spinning tyre though! ;)
May
13
comment Help getting the distance an object has moved
not only was the question very close to being a "do my homework" type question anyway, clearly not permitted in the FAQ, but your answer has gone one step further and does it. Hence why I phrased my attempt more as a guide than complete calculation.
May
13
comment Maxiumum weight a buoy can float
@Georg - The volume of pressurized are is not meaningless; it has a mass associated with its volume and density. However, I was assuming the walls of the buoy were thin, and the air wasn't significantly pressurized (since this would have a detrimental effect on the buoyancy anyway.) Perhaps I could have stated this but I didn't want to overcomplicate a brief comment.
May
13
comment Maxiumum weight a buoy can float
Buoyancy is related to the weight of the volume of material displaced. In your case this means the max weight would be equal to $3943mm^3$ of water, minus the 0.8kg weight of the buoy..