Physics marathon (hsc) (1 Viewer)

[steero1]

Can someone tell me how you draw pnp and npn transistors fully labelled please.

 

[Parvee]

a mass*

lol

Its object

For this question its best to take your definition straight from the syllabus:
define gravitational potential energy as the work done to move an object from a very large distance away to a point in a gravitational field

 

[bleakarcher]

Its object

For this question its best to take your definition straight from the syllabus:
define gravitational potential energy as the work done to move an object from a very large distance away to a point in a gravitational field

lol shit, I didn't know. I thought they would have marked you down for saying object..

 

[barbernator]

Define g-force (1 mark)

Outline THREE safety mechanisms used within a rocket during its launch into a stable orbit to protect the astronaut from excessive g-forces. (3 marks)

 

[zeebobDD]

Define g-force (1 mark)

Outline THREE safety mechanisms used within a rocket during its launch into a stable orbit to protect the astronaut from excessive g-forces. (3 marks)

alrite ima join in on this,

i) G-force is the force experienced by the astronauts relative to the earths gravitational field

ii) The positioning on the astronauts ;upright, duno about other 2:/

 

[bleakarcher]

Define g-force (1 mark)

Outline THREE safety mechanisms used within a rocket during its launch into a stable orbit to protect the astronaut from excessive g-forces. (3 marks)

I can answer the first part (I think haha). Is 'g-force is a measure of the ratio of the apparent weight of an object to its true weight' sufficient?

 

[barbernator]

I can answer the first part (I think haha). Is 'g-force is a measure of the ratio of the apparent weight of an object to its true weight' sufficient?

I want MOAR. what is apparent and true weight?

 

[Danstar2]

Define g-force (1 mark)

Outline THREE safety mechanisms used within a rocket during its launch into a stable orbit to protect the astronaut from excessive g-forces. (3 marks)

1. G-Force may be defined as a whole integer in multiples of 9.8m/s/s. E.g. 2g's = (2x9.8m/s/s). Fg= g+a/g. Where G-Force is equal to 9.8m/s/s + acceleration / 9.8m/s/s

2. - Lay the Astronaut as to apply gforce vertically downwards over the body lying horizontally. This stops red or black outs. Allows the astronaut to experience greater g's without having a major effect.
- Lowering the acceleration with lower the gforce experienced

Not sure, I don't really know 3 significant factors.

 

[barbernator]

lol shonga just realised

the three I was going to say are (spoiler alert highlight below)

g-force = apparent weight/true weight. Apparent weight is the sum of the contact forces acting on a body, and true weight is the normal force on the body when it is stationary on the earth's surface

- Eyes in instead of eyes out approach, and this transverse application of force ensures that blood stays in the brain
- Specially designed suits that support and mold to the astronauts body to ensure minimal stress on body
- Multi stage rocket shutdown to minimise the peak g-force the astronaut is subject to

 

[Danstar2]

True weight is F=MA by gravity. I think apparent weight is Fg= g+a/g, which is your apparent weight plus the force associated with your acceleration, a.

 

[Danstar2]

Explain the function of PNP transistors and how they work.

Sorry for double post.

 

[bleakarcher]

I want MOAR. what is apparent and true weight?

lol, thought it wasn't clear enough too.

 

[someth1ng]

Define g-force (1 mark)

Outline THREE safety mechanisms used within a rocket during its launch into a stable orbit to protect the astronaut from excessive g-forces. (3 marks)

1. g-force is a representation of apparent weight as a proportion of true weight where F(apparent)=m(a+g) and F(true)=mg

2. Firstly, the orientation of astronauts is such that they are lying down such that the rocket's acceleration is perpendicular to their body because transverse acceleration is much more tolerable than longitudinal acceleration towards the head or feet, preventing black or red outs respectively. Transverse accelerations allow the astronaut to tolerate up to about 10g. Furthermore, multi-stage rockets are used because as mass of the rocket decreases, acceleration increases where force on the rocket by fuel burning is constant (F=ma) and hence, g-force increases. Multi-stage rockets prevent extremes in g-forces from being experienced by astronauts. Finally, astronauts are seated on specially contoured recliners which are an extra safety measure to prevent astronauts from being forced into dangerous orientations due to excessive g-forces.

 

[barbernator]

Explain the function of PNP transistors and how they work.

Sorry for double post.

A PNP transistor is used to either amplify a signal, act as a switch to stop current flow, or as a rectifier to ensure unidirectional current. The conjunction of 2 diodes (insert diagram of Emittor, Base and Collector and the 2 circuits) can be biased appropriately to perform each these functions, as controlling the bias within one circuit will result in a change in current flow through the second circuit. The interaction of the depletion zones affects the ability of current to flow. (sorry this description is very hazy, but I don't think it is required in the syllabus, not sure)

 

[Danstar2]

Explain how superconductors are used in Maglev trains, and also name 2 other uses for superconductors.

 

[nightweaver066]

Define g-force (1 mark)

Outline THREE safety mechanisms used within a rocket during its launch into a stable orbit to protect the astronaut from excessive g-forces. (3 marks)

1. The ratio of vertical acceleration to gravitational acceleration on an object.

2. - The astronaut is seated in a reclined, contour couch seat facing the direction of acceleration such that they experience lateral g-force loads. An "eyeballs in" force is easier to cope with than an "eyeballs out" force, prevents black outs and red outs reducing stress on astronaut
- Rocket undergoes braking ellipses prior re-entering to slow down re-entry speed reducing excessive g-forces on the astronaut
- Optimum re-entry angle also for the above reason

 

[barbernator]

1. The ratio of vertical acceleration to gravitational acceleration on an object.

2. - The astronaut is seated in a reclined, contour couch seat facing the direction of acceleration such that they experience lateral g-force loads. An "eyeballs in" force is easier to cope with than an "eyeballs out" force, prevents black outs and red outs reducing stress on astronaut
- Rocket undergoes braking ellipses prior re-entering to slow down re-entry speed reducing excessive g-forces on the astronaut
- Optimum re-entry angle also for the above reason

for part 2. they are correct but the question says "during its launch into a stable orbit"

 

[someth1ng]

for part 2. they are correct but the question says "during its launch into a stable orbit"

Yeah, I noted that too...you got there first

 

[nightweaver066]

Explain how superconductors are used in Maglev trains, and also name 2 other uses for superconductors.

Some maglev trains employ electrodynamic suspension (EDS) which involves the use of electromagnets and superconductors. Electromagnets are placed across train tracks and are powered by three-phase AC current to produce a dynamic magnetic field, interacting with the superconductors at the bottom of the train via the Meissner effect (superconductors generates persistent currents of equal depth of magnetic field penetration to repel all magnetic flux) causing the train to levitate and accelerate. EDS in particular stabilises the train's motion lessening the need for maintenance and monitoring.
2 other uses: MRIs & particle accelerators.

for part 2. they are correct but the question says "during its launch into a stable orbit"

Thanks, I've really got to read questions..

Outline the Braggs experiment in determining the crystal structure of material.

 

[someth1ng]

nightweaver066, I must confess myself...disappointed.

The Meissner effect has nothing to do with Maglev trains.

In Maglev trains, there is electrodynamic suspension (EDS) and electromagnetic suspension (EMS) systems. EDS is magnetic levitation by repulsion on the train while EMS is magnetic levitation by attraction on the train. The coils used to produce magnetic flux may be superconductors as they have no resistance. This allows very high currents to pass through the coil to produce very powerful magnetic fields and hence, allow the train to levitate. An AC current is supplied with a frequency corresponding to the train's velocity to constantly apply a pulling and pushing force using strong magnetic fields on the train.