Physics marathon (hsc) (8 Viewers)

[adzlark]

Guys, maglev trains are NOT levitated due to the meissner effect.

What about the EDS system in Japan? I understand the EMS system is purely electromagnetic repulsion. But I was under the impression that the EDS system levitated by means of the meissner effect.

 

[freeeeee]

A Maglev train relies on superconductors for operation, superconductors are utilised both to levitate the maglev train and to propel the train. On the rails of a maglev train situate superconducting electromagnets which are fed with AC current, this means that the electromagnets have constantly changing polarity so they will alternately be pulled by magnets infront and pushed by magents behind. While on the train, superconducting coils are fed with large DC current setting up a strong constant magnetic field. The relative forward motion of the train causes changing flux in the coils on the train inducing large eddy currents, repelling the train, causing it to levitate.

This is how they operate right? confirmation pls

 

[barbernator]

What about the EDS system in Japan? I understand the EMS system is purely electromagnetic repulsion. But I was under the impression that the EDS system levitated by means of the meissner effect.

Nope, the superconducting wire in the solenoid on the train is purely just to make a stronger repulsive magnetic field. The mass of the train is WAY to heavy for the meissner effect to be used to levitate, as the force of gravity would result in the current in the superconductors being too large and causing the magnets to lose their superconducting properties.

 

[barbernator]

This is how they operate right? confirmation pls

nope.

1. Superconductors are only used in levitation
2. Superconductors are on the train and not the rails.
3. They are not fed with AC current, they are fed with DC current yet alternated by a switch.
4. large eddy currents are not formed, there is just a constant repulsion between the current in the wire on the train and the electromagnets underneath.

 

[dawooddaman]

Maglev trains are trains that are not in contact with the ground due to the use of electromagnets for levitation and propogation

There are 2 types of maglev trains currently in operation, Electrodynamic suspension and electromagnetic suspension systems.

(ill just discuss EDS cos its the only one with superconductors)

For levitation, on the track, electromagnets are used that are not superconducting, just regular magnets. On the train, superconducting wire is used in the electromagnet to allow large currents to flow and hence create a powerful magnetic field. These are cooled by liquid nitrogen. By making the electromagnets repel each other (either by N facing N or S facing S) the train is able to levitate. (diagram)

For propulsion, equal strength electromagnetic interaction by magnets on the train and to the left and right of train are required. The electromagnets on the train are of fixed poles, while the electromagnets on the track are constantly alternating poles to create attraction and repulsion in phase with the motion of the train, necessary to either accelerate or decelerate the train. (diagram is a must)

Through these two sets of electromagnetic interaction, maglev trains are able to both levitate and be moved along a track.

Thanks buddy

 

[freeeeee]

nope.

1. Superconductors are only used in levitation
2. Superconductors are on the train and not the rails.
3. They are not fed with AC current, they are fed with DC current yet alternated by a switch.
4. large eddy currents are not formed, there is just a constant repulsion between the current in the wire on the train and the electromagnets underneath.

Great thanks

 

[adzlark]

Question: In 1970 NASA launched Apollo 13, their third mission planned to land humans on the Moon. Half-way to the Moon a huge explosion crippled the spacecraft. The only way home for the astronauts was to fly around the back of the Moon and then fire the rocket engine to take the craft out of lunar orbit and put it into an Earth-bound trajectory.

At the completion of the rocket engine burn Jim Lovell said "We just put Isaac Newton in the driver's seat."

Given that the spacecraft returned to Earth safely, justify Lovell's statement.

 

[Danstar2]

Question: In 1970 NASA launched Apollo 13, their third mission planned to land humans on the Moon. Half-way to the Moon a huge explosion crippled the spacecraft. The only way home for the astronauts was to fly around the back of the Moon and then fire the rocket engine to take the craft out of lunar orbit and put it into an Earth-bound trajectory.

At the completion of the rocket engine burn Jim Lovell said "We just put Isaac Newton in the driver's seat."

Given that the spacecraft returned to Earth safely, justify Lovell's statement.

Newton's Law of Universal Gravitation would suggest that there is a gravitational attraction between the moon and the spacecraft. Thus, using minimal energy the rocket was able to use planetary swingby around the moon, using the moons gravitational field F=MA as a force to effectively pull the spacecraft. The spacecraft uses the gravitational field which is equal to centripetal force, to travel around the curvature of the moon and change the spacecraft's trajectory relative to the earth, to return home safely.

Something like that?

 

[nerdasdasd]

Newton's Law of Universal Gravitation would suggest that there is a gravitational attraction between the moon and the spacecraft. Thus, using minimal energy the rocket was able to use planetary swingby around the moon, using the moons gravitational field F=MA as a force to effectively pull the spacecraft. The spacecraft uses the gravitational field which is equal to centripetal force, to travel around the curvature of the moon and change the spacecraft's trajectory relative to the earth, to return home safely.

Something like that?

You forgot newtons 3rd law.

 

[barbernator]

Newton's Law of Universal Gravitation would suggest that there is a gravitational attraction between the moon and the spacecraft. Thus, using minimal energy the rocket was able to use planetary swingby around the moon, using the moons gravitational field F=MA as a force to effectively pull the spacecraft. The spacecraft uses the gravitational field which is equal to centripetal force, to travel around the curvature of the moon and change the spacecraft's trajectory relative to the earth, to return home safely.

Something like that?

you could also talk about the equal and opposite reaction from the burning of fuel. something like "the propulsion of the gas particles in the fuel when burnt provided an equal and opposite force that propelled the rocket towards earth (newton's third law)"

 

[RishBonjour]

anyone good in medical physics MRI section? really struggling.

 

[nucgaek]

"Explain how the slingshot effect works with relation to the COE, and describe its implications on spaceflight."

Kinda similar to the other one on Newton but how would you describe the effect in more detail?

 

[manscux]

Is this not paradoxical:

we understand that mass dilates at the speed of light (i.e mass dilation) due to the momentum equation.. ie mv = mc for two particles travelling towards each other..... in an inertial reference fram the mass would have to decrease of the particle traveling at speed of light

But as velocity increase the equivalence between mass and energy tells us that extra engery is equated to mass... thus at c mass increases....

how can mass dilate and increase?

 

[dawooddaman]

Is this not paradoxical:

we understand that mass dilates at the speed of light (i.e mass dilation) due to the momentum equation

But as velocity increase the equivalence between mass and energy tells us that extra engery is equated to mass... thus at c mass increases....

how can mass dilate and increase?

Absorbs energy and converts in mass, vice versa

 

[jax447]

Question: In 1970 NASA launched Apollo 13, their third mission planned to land humans on the Moon. Half-way to the Moon a huge explosion crippled the spacecraft. The only way home for the astronauts was to fly around the back of the Moon and then fire the rocket engine to take the craft out of lunar orbit and put it into an Earth-bound trajectory.

At the completion of the rocket engine burn Jim Lovell said "We just put Isaac Newton in the driver's seat."

Given that the spacecraft returned to Earth safely, justify Lovell's statement.

ridiculous question

 

[nucgaek]

What are all of the different types of motor/generator we need to know? Also, what are their differences/simiarities?

 

[LlamaBoi]

how can mass dilate and increase?

to dilate means to increase, dont get confused

 

[Danstar2]

anyone good in medical physics MRI section? really struggling.

Yes I can help a bit, depends what the question is.


@Barbernator, thanks I remember that, I forgot to mention it The positive momentum of the rocket is equal to negative momentum of the gases.


how can mass dilate? E=Mc^2

 

[barbernator]

ridiculous question

well it was in 2005 HSC. and its not ridiculous, it just requires thinking which is what students should be able to do.

 

[RishBonjour]

well it was in 2005 HSC. and its not ridiculous, it just requires thinking which is what students should be able to do.

hope 2012 exam is like this - 90% of my cohort will stuff up though. (except hole flow lol - don't understand that)