HSC Physics Question Thread

[JemexR]

A quick simple question; does HSC specify acceleration due to gravity as 9.8 or 10 ms-2?

[Cindy2k16]

A quick simple question; does HSC specify acceleration due to gravity as 9.8 or 10 ms-2?

9.8 usually. unless the question specifies otherwise
Sometimes the projectile is on a different planet with a different gravitational field. If this is the case they'll usually say what the acceleration due to gravity is, unless the question is to find the acceleration due to gravity.

[RuiAce]

A quick simple question; does HSC specify acceleration due to gravity as 9.8 or 10 ms-2?

Furthering onto what Cindy said

If you look on your data sheet for physics, it clearly states that g = 9.8

[JemexR]

Furthering onto what Cindy said

If you look on your data sheet for physics, it clearly states that g = 9.8

hehe. Sorry for that waste of time...

[RuiAce]

hehe. Sorry for that waste of time...

Well if you were genuinely unsure then it's not a waste of time and just clearing up little bits and pieces, so all good

[FallonXay]

Hellloooooooooo! 

How would you work out this question? (Bostes answers say D; The excel Success One Physics book answers say B)

Thanks!!!

[noonedoesnt]

Hellloooooooooo! 

How would you work out this question? (Bostes answers say D; The excel Success One Physics book answers say B)

Thanks!!!

This was an extremely controversial question, and from what I heard the answer D was a violation of conservation of energy, but i'm not too sure about that. Anyways I feel D makes no sense in answering that question, because if he is outside a spacecraft in orbit, both have the same orbital radius and the same period. Thus B would be correct.

[FallonXay]

This was an extremely controversial question, and from what I heard the answer D was a violation of conservation of energy, but i'm not too sure about that. Anyways I feel D makes no sense in answering that question, because if he is outside a spacecraft in orbit, both have the same orbital radius and the same period. Thus B would be correct.

Ahh k. Cheers 

[FallonXay]

Hello again,

How would you answers this question?

Thanks in advance~ 

[MysteryMarker]

Hey guys,

For Hertz' experiment to demonstrate the production/existence of radio waves, for the transmitter coil I've read that he used a high voltage AC power source connected to an induction coil and so on... But for the 2008 physics Q which asks us to 'describe an investigation used to demonstrate the production and reception of radio waves' they utilised a DC power supply. Does it matter whether AC or DC is used?

Cheers.

[jakesilove]

Hello again,

How would you answers this question?

Thanks in advance~ 

Hey! You needed to break down this answer into three parts; launch, slingshot, and orbit.

For launch, discuss conservation of momentum. Explain how we launch rockets, and how we optimise speed etc. You don't need to go into too much depth here, but if you can outline escape velocity that would be ideal.

Then, the slingshot effect. Explain how it works, draw a diagram, and explain why we use it. Simple.

Finally, orbit. Explain orbital velocity, throw in some laws of gravitation, discuss friction etc. and you're golden!

[jakesilove]

Hey guys,

For Hertz' experiment to demonstrate the production/existence of radio waves, for the transmitter coil I've read that he used a high voltage AC power source connected to an induction coil and so on... But for the 2008 physics Q which asks us to 'describe an investigation used to demonstrate the production and reception of radio waves' they utilised a DC power supply. Does it matter whether AC or DC is used?

Cheers.

Nope

[jamonwindeyer]

Hellloooooooooo! 

How would you work out this question? (Bostes answers say D; The excel Success One Physics book answers say B)

Thanks!!!

This was an extremely controversial question, and from what I heard the answer D was a violation of conservation of energy, but i'm not too sure about that. Anyways I feel D makes no sense in answering that question, because if he is outside a spacecraft in orbit, both have the same orbital radius and the same period. Thus B would be correct.

When in doubt; BOSTES solution wins. The Success One Physics Book has quite a few errors; my tutoring students and I find them fairly frequently. The answer here is indeed D. But yep, it's a weird one!

The fact that both the spacecraft and astronaut are in orbit with the earth around the sun makes no difference; the effects of the suns gravity are negligible compared to the other forces at play in this scenario. B just doesn't make sense; it's just stating an irrelevant fact. A is incorrect; clearly gravity has to play a significant role if we have an orbit

Would C be correct? Well the force of gravity on each is:



The mass of the astronaut is different to the mass of the spacecraft, so the forces are different. So C is incorrect too. That leaves D by process of elimination.

The actual reason is this, consider Newton's 2nd Law:



So the acceleration of the astronaut and the spacecraft is:



Acceleration is inversely proportional to mass, and this is why the accelerations are identical, because substituting the expression for gravitational force yields:



Mass plays no role, so their acceleration will be the same, meaning they'll have the same orbit

[imtrying]

Hi! Sorry if this has already been answered, but how do I do Q12 in the 2011 HSC?
https://www.boardofstudies.nsw.edu.au/hsc_exams/hsc2011exams/pdf_doc/2011-hsc-exam-physics.pdf

[FallonXay]

When in doubt; BOSTES solution wins. The Success One Physics Book has quite a few errors; my tutoring students and I find them fairly frequently. The answer here is indeed D. But yep, it's a weird one!

The fact that both the spacecraft and astronaut are in orbit with the earth around the sun makes no difference; the effects of the suns gravity are negligible compared to the other forces at play in this scenario. B just doesn't make sense; it's just stating an irrelevant fact. A is incorrect; clearly gravity has to play a significant role if we have an orbit

Would C be correct? Well the force of gravity on each is:



The mass of the astronaut is different to the mass of the spacecraft, so the forces are different. So C is incorrect too. That leaves D by process of elimination.

The actual reason is this, consider Newton's 2nd Law:



So the acceleration of the astronaut and the spacecraft is:



Acceleration is inversely proportional to mass, and this is why the accelerations are identical, because substituting the expression for gravitational force yields:



Mass plays no role, so their acceleration will be the same, meaning they'll have the same orbit

Ahh k, gotcha. Thanks