Physics Marathon 2012 (2 Viewers)

[someth1ng]

^ That's a good and solid answer. I would suggest explicitly stating that the problem of the first thought experiment was that it violated the laws of special relativity then explain that Einstein believed that relativity should always hold true. Also, I would also suggest keeping in the order of the question. By the order, I mean, describe the problems with the thought experiment then describe what would happen in reality as according to Einstein.

 

[jenslekman]

Discuss the BCS theory in detail

 

[barbernator]

Discuss the BCS theory in detail

not really possible seeing as it is so fleetingly touched on in the syllabus haha

 

[barbernator]

^ That's a good and solid answer. I would suggest explicitly stating that the problem of the first thought experiment was that it violated the laws of special relativity then explain that Einstein believed that relativity should always hold true. Also, I would also suggest keeping in the order of the question. By the order, I mean, describe the problems with the thought experiment then describe what would happen in reality as according to Einstein.

good suggestion, I see what u mean.

 

[barbernator]

I will give it a crack, superconductivity is the one area I need to revise the most, but here we go.

The BCS theory suggests that when a superconductive material is cooled below its critical temperature, the electrons experience no resistance within the positive lattice of the material. The vibrations of the positive lattice within a material produce energy waves called phonons. When the metal is cooled below its critical temperature, the energy of these phonons are absorbed by a pair of electrons, allowing them to overcome their electrostatic repulsion. As positive and negative charges attract, this causes the positive lattice to bend toward an electron when it is moving. The cooper pair negates this bending effect, as the pair creates a form of "push - pull" relationship (insert diagram here of electron either side of positive squeezed lattice) in which the effect of the positive lattice on the electron is zero and no energy is lost and it becomes a perfect conductor that doesn't lose heat to its surroundings.

 

[barbernator]

next question.

Explain in depth how power transmission lines are protected from lightning strikes and are insulated from electrical arcing.

 

[someth1ng]

not really possible seeing as it is so fleetingly touched on in the syllabus haha

Agreed, you'll also need diagrams to do it well which is a bit of a pain.

Compare low-earth amd geostationary orbits.

 

[someth1ng]

next question.

Explain in depth how power transmission lines are protected from lightning strikes and are insulated from electrical arcing.

This isn't in detail because I'm on my iPod so I'll keep it brief.

Lightning strikes and electrical arcs are a problem because it can severly affect power transmission from a supplier to a consumer, damage equipment at the substations, pole transformers and household equipment and increase the already high electrical losses.

Power lines are protected from lightning strikes by using shield conductors. Shield conductors are open wires that are connected directly to a metal transmission tower while usually carrying no current. Shield conductors can be found at the top of metal transmission towers and because light has a tendency to strike the highest point of a structure, the shield conductors will be struck and electricity channelled to the ground before power lines are affected.

(Insert image of an "iron man")

Electrical arcing is minimised by fully insulating all current carrying wires and using suspension insulators. Suspension insulators are made of ceramic insulating discs which increase the distance between the tower and the transmission lines which carry very high voltages. Increasing the distance between the transmission lines and the metal tower disallows sparks from being produced between them. In addition, the increase in distance also causes less eddy currents to be induced in the tower due to the constantly changing magnetic flux made by the AC electricity in the transmission lines - this improves efficiency of power transmission.

(Insert image of suspension insulators)

 

[barbernator]

Agreed, you'll also need diagrams to do it well which is a bit of a pain.

Compare low-earth amd geostationary orbits.

A low earth orbit is an orbit within the range of 300km to 1000km above the earth's surface. The period of objects in this orbital range are around 1 hour. Low earth orbit satellites experience high air resistance, and, must be boosted often in order to maintain their circular orbit and avoid orbital decay. The speed of satellites in low earth orbit is around -----km (insert calculation from formula here cbf)
A geostationary orbit is an orbit with a period of exactly 1 day at an altitude of 36500km. As a result, geostationary orbits remain fixed to a single spot above the earth on the equator. (side note) geosynchrinous orbits do not orbit around the equator. A geostationary orbit is at a sufficient altitude such that the atmospheric drag is negligible and the orbit will almost never decay. The orbital velocity of a geostationary orbit is much slower than a low-earth orbit at ----km (again cbf). Each orbit has its advantages for communication and other purposes. A geostationary orbit is used for GPS and communication satellites, whereas a low earth orbit can be used for objects that are in orbit for a temporary basis, to minimise the fuel required to get satellites into the orbit. An example includes the international space station, as it would be too expensive to get astronauts into a geostationary orbit.

 

[Living Moment]

Yea Physics!!! I'm new here and don't know how to put up Q. like the first post and how do I make Equations on the post? =)

 

[barbernator]

Yea Physics!!! I'm new here and don't know how to put up Q. like the first post and how do I make Equations on the post? =)

http://www.codecogs.com/latex/eqneditor.php might take a bit of jigging but you'll get used to it.

 

[barbernator]

also, I have one of the best projectile motion questions for physics, please don't try and use X1 to make it easier.

An object is fired at an angle of 15 degrees to the horizontal. It hits the ground 7m from its starting point. Find its initial velocity. (g=-9.8ms-2)

 

[Living Moment]

Thanks and how do I put a Q. on my actual post without a link like the first guy did?

 

[barbernator]

[IMG ] [/IMG ] do that at the start and end of the uploaded image without the spaces

 

[Living Moment]

Thanks brother have my physics trail/practical exam on Thursday, and after that we'll get this physics marathon started, btw are you allowed to put CSSA/Indep Q. NOT papers?, because I heard people around here are abit scared of big man =/

 

[barbernator]

Thanks brother have my physics trail/practical exam on Thursday, and after that we'll get this physics marathon started, btw are you allowed to put CSSA/Indep Q. NOT papers?, because I heard people around here are abit scared of big man =/

yeh you're allowed to post questions from past CSSA and independent papers

 

[Parvee]

also, I have one of the best projectile motion questions for physics, please don't try and use X1 to make it easier.

An object is fired at an angle of 15 degrees to the horizontal. It hits the ground 7m from its starting point. Find its initial velocity. (g=-9.8ms-1)

Disappointed

 

[barbernator]

Disappointed

I am disappoint that you haven't answered the question... but fixed hahaha

 

[Parvee]

I am disappoint that you haven't answered the question... but fixed hahaha

Is the answer 11.71ms-1?

 

[barbernator]

Is the answer 11.71ms-1?

correctamundooooo