595 reputation
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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


Jun
30
comment maximum rotational speed
@Marek's answer in @voix's linked-question seems to answer it for me. Good question all the same :-)
Jun
30
comment how does dynamic casimir effect generate correlated photons
Great question +1. I'm left wondering if measuring the flux of the photons produced could be used as a measure of some part of the vacuum energy spectrum?
Jun
30
comment Does a static electric field and the conservation of momentum give rise to a relationship between $E$, $t$, and some path $s$?
@yayu: indeed, particulry @Andrew's answer and the associated paper. Thanks
Jun
30
comment Does a static electric field and the conservation of momentum give rise to a relationship between $E$, $t$, and some path $s$?
Maybe I'm being stupid but surely if you could consider an object that has no net force acting on it, you would get 0 if you just took any loop integral around it: ∮pho⋅ds=0 What would one call the 'force field' be called though?
Jun
30
comment On a bicycle, why does my back tyre wear so much more quickly than the front?
@bubble: No, it was the incorrect physics that persuaded me.
Jun
30
comment On a bicycle, why does my back tyre wear so much more quickly than the front?
Sorry but there are a couple of incorrect assertions and even more spelling mistakes in this, hence a -1 I'm afraid.
Jun
29
comment Collision between a rod and a bullet
@Willie: I see what your saying, I hadn't thought of it that way but now you mention it I agree that two collisions could be possible.
Jun
29
comment Collision between a rod and a bullet
Interesting question. My 'hunch' would be that if the rod is indeed considered "rigid" (which is obviously not physical) the maximum number of collisions would be one. That said, I'm not sure I personally am capable of showing this using conservation of linear and angular momentum. I'll try a little back-of-an-envelope calculation later this afternoon..
Jun
28
accepted Hail stones in summer?
Jun
28
comment What if the LHC doesn't see SUSY?
Very interesting reading @Lawrence (+1.) @anna I just wondered if you had an opinion on 'proton-driven plasma wakefield accelerators'? See pg 18 on the slides of this recent talk for example: c-ad.bnl.gov/pac2011/proceedings/talks/tuobn5_talk.pdf Could this scheme ever be implemented in the main LHC tunnel in the years to come, and what energy lepton beams might this offer?
Jun
24
asked Hail stones in summer?
Jun
24
comment Why is the decay of neutral kaons (violates CP invariance) seemingly not sufficient enough for certain people to describe matter-antimatter imbalance?
+1 for "..this is a family site." Haha
Jun
24
comment Does particle indistinguishability and quantised enery levels (in bound states) violate the Pauli Exclusion Principle?
@Gigacyan: Sure is, duly accepted. Cheers
Jun
24
accepted Does particle indistinguishability and quantised enery levels (in bound states) violate the Pauli Exclusion Principle?
Jun
22
comment electron orbits
Hyperphysics has a nice exposition on this: hyperphysics.phy-astr.gsu.edu/hbase/hyde.html
Jun
22
comment electron orbits
@dmckee: I did say it was a simplistic answer ;-)
Jun
22
comment Ascent rate and size of balloon
@Cameron: You could calculate a rough estimate by doing a little experiment - Get one of the balloons you intend to use and inflate it until it pops. If you know the pressure difference between inside and out when it pops, you could predict at what height this same pressure difference would occur. Since measuring the pressure in the balloon may be difficult in practise, you could calculate it if you measured the size and (negative) weight of the balloon, up until the moment it bursts.
Jun
22
comment electron orbits
A simplistic answer: if a single electron, bound to a proton, absorbs a photon, the electron will be excited into a higher energy state. If the photon absorbed is higher than the ionization energy, the electron will be liberated from the atom. Therefore the highest energy state the electron could occupy, without being ionised, would be the state closest to the ionization energy (from below.)
Jun
22
comment Function of electric water pump
That just depends on which way around you connect the two pipes to it.
Jun
21
comment Energy produced by a swing?
Hi @Seb, the GPE and KE are the two forms the energy could be in. The total energy available in the system is $E=GPE+KE$. When the swing is high it is changing direction, which implies the velocity is zero and therefore the KE is zero. All the total energy is therefore all in the form of the GPE at this moment. When the swing is low, the velocity is maximum, and therefore so is the KE. The GPE is necessarily zero at this point. All of E, GPE and KE are energies - so yes, they are all measured in Joules.