HSC Physics Marathon 2016 (3 Viewers)

[leehuan]

Could you please explain what you mean by this or provide an example


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To assess is to simply provide your stance, i.e. do you agree or disagree, to what extent can an aforementioned statement be true

 

[Glyde]

Ohhh so I could say the this statement is genuinely accurate however the vectors of which these two planets attract are in opposite directions?


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[Glyde]

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[Glyde]

New question : Explain why the object used for slingshot motion (planet, star, etc...) needs to be moving.

How many marks would this question be. Also is there any rule to follow in relation to marks per question ? Should I approach questions differently in relation to there given marks ?


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[RachelGreen]

Could you please explain what you mean by this or provide an example


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Once you've written all of your points to back up your opinion. Simply write a judgement like for say "This statement is invalid". I don't think you have to explain why it's invalid since you have already written a lot of points on why it's invalid above. This is just an example

 

[Glyde]

Once you've written all of your points to back up your opinion. Simply write a judgement like for say "This statement is invalid". I don't think you have to explain why it's invalid since you have already written a lot of points on why it's invalid above. This is just an example

Wow that's worth a whole mark ?


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[InteGrand]

Wow that's worth a whole mark ?


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Yeah, since the Key Word is "assess", which means you need to make a judgement.
Assess: "Make a judgement of value, quality, outcomes, results or size"

( The BOSTES definitions of key words is found here, and you should be familiar with them http://www.boardofstudies.nsw.edu.au/syllabus_hsc/glossary_keywords.html )

 

[leehuan]

You would be surprised how many candidates lose the mark for making a judgement every year

 

[Glyde]

New question : Explain why the object used for slingshot motion (planet, star, etc...) needs to be moving.

When an object such as a space probe approaches a planet, it is accelerated by the larger mass' gravitational pull, this statement is often misinterpreted as the source of the slingshot effect. However when the space probe continues back out of the planets atmosphere it will again be effected by the planets gravitational field but in the opposite direction. It will begin to decelerate back down to its initial velocity. The thing that actually causes the slingshot effect is the fact that the planet is orbiting something else, such as the sun. Hence when the space probe enters the planets atmosphere or gravitational pull it is accelerated to the planets orbitory speed around the sun. This causes the vectors of the space probes initial velocity and the planets orbitory velocity around the sun to add, consequently resulting in an angle change and velocity change. It is also important to note that the original misconception does not cause a slingshot effect due to the conservation of momentum. The space probe received an additional speed boost causing the planet to slow down. This is not noticeable because the planets mass is usually a lot bigger then the space probes mass hence having little effect of the planets speed. Similarly the space probe is slowed down to its original speed and the planet is sped up to its original speed.


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[leehuan]

When an object such as a space probe approaches a planet, it is accelerated by the larger mass' gravitational pull, this statement is often misinterpreted as the source of the slingshot effect. However when the space probe continues back out of the planets atmosphere it will again be effected by the planets gravitational field but in the opposite direction. It will begin to decelerate back down to its initial velocity. The thing that actually causes the slingshot effect is the fact that the planet is orbiting something else, such as the sun. Hence when the space probe enters the planets atmosphere or gravitational pull it is accelerated to the planets orbitory speed around the sun. This causes the vectors of the space probes initial velocity and the planets orbitory velocity around the sun to add, consequently resulting in an angle change and velocity change. It is also important to note that the original misconception does not cause a slingshot effect due to the conservation of momentum. The space probe received an additional speed boost causing the planet to slow down. This is not noticeable because the planets mass is usually a lot bigger then the space probes mass hence having little effect of the planets speed. Similarly the space probe is slowed down to its original speed and the planet is sped up to its original speed.


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Question not fully answered though; since he's asking for why it must be moving you must also explain what the problem will be when the space probe is somehow at rest.

The bolded part must be emphasised, but the misconception that you gave can be made very brief

 

[Glyde]

3/4?


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[Glyde]

Question not fully answered though; since he's asking for why it must be moving you must also explain what the problem will be when the space probe is somehow at rest.

The bolded part must be emphasised, but the misconception that you gave can be made very brief

If the object is at rest it will just obviously fall....


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[leehuan]

If the object is at rest it will just obviously fall....


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That's all you had to say. It can't pick up momentum from the sun and instead it will fall.

Hence why I said logic. But always answer the question. Also, tbh, you could relate p=mv

 

[Glyde]

Cannonballs P and Q are fired so that they leave their barrels from the same height. Cannonball P is fired vertically upwards while cannonball Q is fired at an acute angle.
Both cannonballs take 3 seconds to reach the same maximum height.

Explain how the resulting motion of the cannonballs supports Galileo’s analysis
of projectile motion. ( 3 marks)


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[RachelGreen]

Galileo was the first to use mathematics to analyse projectile motion. He considered that, rather than using the motion of the object as a whole, it could be split into the constituent vertical and horizontal components (note that they're independent of each other), and when added together as vectors, it produced the total velocity of the object. He realised that the only external force acting on this object is gravity, and would only influence the vertical motion of the object while the horizontal velocity of the object would sty constant. Both balls would experience the same acceleration due to gravity regardless of mass (this is assuming no resistance), and hence would reach the same height, and strike the ground at the same time (as would objects of different mass).

Didn't really understand it much, correct me if I'm wrong

 

[leehuan]

Galileo was the first to use mathematics to analyse projectile motion. He considered that, rather than using the motion of the object as a whole, it could be split into the constituent vertical and horizontal components (note that they're independent of each other), and when added together as vectors, it produced the total velocity of the object. He realised that the only external force acting on this object is gravity, and would only influence the vertical motion of the object while the horizontal velocity of the object would sty constant. Both balls would experience the same acceleration due to gravity regardless of mass (this is assuming no resistance), and hence would reach the same height, and strike the ground at the same time (as would objects of different mass).

Didn't really understand it much, correct me if I'm wrong

Basically yes.
- Horizontal and vertical seperate
- Only force is gravity and acceleration due to gravity was constant
- Relates the question back to these concepts

3/3

 

[RachelGreen]

NEXT QUESTION:
The centripetal force required to keep a satellite in orbit around a planet is provided by the gravitational attraction between the planet and the satellite.
Compare a low earth orbit satellite to a geostationary satellite, and in your own answer explain why geostationary satellites are less susceptible to orbital decay. (3 marks)

 

[MilkyCat_]

A LEO satellite has an altitude of 300-1000km and an orbital period of approximately 90 minutes. On the other hand, a geostationary satellite has an altitude of 36,000km and an orbital period of 23hr 56min, which matches the earth's rotation. Both types of satellites require an extremely high orbital velocity, which depends on the satellites's radius and mass of the earth (insert orbital velocity formula). Due to the smaller radius between the LEO satellite and the earth, the orbital velocity is much higher at 8km/s compared to the geostationary's velocity of 3km/s.

LEO Satellites orbit at altitudes of less than 1000km, while the atmosphere extends out to 9600km where molecules of gas are still present, meaning there is some atmospheric drag leading to friction, resulting in a loss in altitude and orbital decay. Geostationary satellites don't experience this decay due to their high altitude.

 

[RachelGreen]

I'll mark you later, I gotta go out soon.

However, in the meantime, NEXT QUESTION:
Discuss some strategies used to minimize fuel consumption of rockets (3 marks).

 

[Drsoccerball]

When an object such as a space probe approaches a planet, it is accelerated by the larger mass' gravitational pull, this statement is often misinterpreted as the source of the slingshot effect. However when the space probe continues back out of the planets atmosphere it will again be effected by the planets gravitational field but in the opposite direction. It will begin to decelerate back down to its initial velocity. The thing that actually causes the slingshot effect is the fact that the planet is orbiting something else, such as the sun. Hence when the space probe enters the planets atmosphere or gravitational pull it is accelerated to the planets orbitory speed around the sun. This causes the vectors of the space probes initial velocity and the planets orbitory velocity around the sun to add, consequently resulting in an angle change and velocity change. It is also important to note that the original misconception does not cause a slingshot effect due to the conservation of momentum. The space probe received an additional speed boost causing the planet to slow down. This is not noticeable because the planets mass is usually a lot bigger then the space probes mass hence having little effect of the planets speed. Similarly the space probe is slowed down to its original speed and the planet is sped up to its original speed.

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This is what I wanted you to realise from this question. All good.