HSC Physics Question Thread

[Aaron12038488]

i have a question- say for example you are required to use escape velocity formula to answer a question. Do you have to derive it as I've heard formulas that are not on the formula sheet must be derived?

[jamonwindeyer]

i have a question- say for example you are required to use escape velocity formula to answer a question. Do you have to derive it as I've heard formulas that are not on the formula sheet must be derived?

I think it depends a little bit on the mark allocation, but almost always you should be fine to just use the formula. Or, they will structure the question to specifically ask for the derivation

[mxrylyn]

does the sentence "When work is done on an object, there is a corresponding change in the kinetic and/or potential energy of the object"

mean that the work done on and object is equal to the potential energy?
And if it is true, is it true only of potential eneergy? or all energies ie. heat energy ect.

[blasonduo]

does the sentence "When work is done on an object, there is a corresponding change in the kinetic and/or potential energy of the object"

mean that the work done on and object is equal to the potential energy?
And if it is true, is it true only of potential eneergy? or all energies ie. heat energy ect.

Hello! Yes, this is true!

Just recall the law of conservation of energy; where no energy can be created nor destroyed. Imagine I drop a ball 20km above the earth's surface, and as that ball begins to fall, its potential energy DECREASES, so to obey this law, kinetic energy INCREASES. Work done normally means changing the energy from one form to another, so applying a certain amount of work to an object will change a certain amount of energy

Remember,
so for work to be done, it must move

For your second question (I hope I interpreted it correctly), energy being converted to heat energy is considered a non-conservative force as it is making energy leave the system (on the ball) and hence slowing down its kinetic energy. If the ball did not have any of these non-conservative forces and just used kinetic and potential energy, then all energy would be would be retained. In short, I don't think so, if I dropped my ball on a windier day, there would be more heat energy produced, even if dropped at the same height.

Hope this helps

[swordkillz]

Would someone be able to explain why space and time become relative if c is constant and justify this statement (3 marks). Most of the information I find online state this fact without justifying with evidence why such is so. Do I link back to the 2 postulates proposed in special relativity? Do I used scientific examples like muons or atomic clocks?

Thank you so much!!

[blasonduo]

Would someone be able to explain why space and time become relative if c is constant and justify this statement (3 marks). Most of the information I find online state this fact without justifying with evidence why such is so. Do I link back to the 2 postulates proposed in special relativity? Do I used scientific examples like muons or atomic clocks?

Thank you so much!!

Hello!

Yes! That is the approach I would go for, and I would specifically mention the thought experiment that uses a mirror. Where if the train was moving, the light would have to travel slightly further than when it was stationary and hence would need time to go slower to accommodate for this. (If this experiment is not ringing any bells, I'd be happy to fully explain it) I'd draw a diagram to fully show this.

I'd justify this exactly like you did, with examples, just make sure you include the results of them (ie the atomic clock that was moving appeared to show time passed slower)

Hope this helps!

[Aaron12038488]

hey! i need help in gathering info on einsteins thought experiment on time dilation. And the equations involved : 2L /c?

[blasonduo]

hey! i need help in gathering info on einsteins thought experiment on time dilation. And the equations involved : 2L /c?

Hello! For time dilation, the only equation involved for that is:



Remember that:
to = the time elapsed for someone who is stationary, observing the moving object
tv = the time elapsed for someone travelling in the object at a certain speed.
v = the speed of the object compared to the speed of light (c).

When you say you need help gathering information, are you saying that you are finding it difficult to search for secondary sources on the topic? If so, here are a few:

https://science.howstuffworks.com/science-vs-myth/everyday-myths/relativity10.htm
http://www.phy.olemiss.edu/HEP/QuarkNet/time.html
https://futurism.com/einsteins-weird-world-of-relativistic-time-dilation/

For secondary sources, remember you still need to look into valid, reliable and accurate sources, and to identify if these links fall into these categories.

a Valid source is one that relates back to the question asked
a Reliable source is when it comes from a reputable source (such as peer-reviewed journals or .gov sites)
an Accurate source is when it can be cross-referenced by a reliable source, and contains consistent information.

If this was not what you were asking, and wanted help on the idea of time dilation itself, sorry!! Just send in another post asking

Hope this helps

[RuiAce]

Hello! For time dilation, the only equation involved for that is:


Hint: Use the underscore to open a subscript

Just thought I'd pop in on the first bit. When he spoke about the 2L/c bit I think he meant this:


(I don't know how any of that works anymore though so if you want to clarify it for him please do)

Although, having said that, pretty sure 2L/c is related to how time dilation actually works and not an equation we actually use for computations

[blasonduo]

Just thought I'd pop in on the first bit. When he spoke about the 2L/c bit I think he meant this:
(Image removed from quote.)
(Image removed from quote.)
(I don't know how any of that works anymore though so if you want to clarify it for him please do)

Although, having said that, pretty sure 2L/c is related to how time dilation actually works and not an equation we actually use for computations

Ahh! That makes more sense! Thanks! but yeah, Rui is right.

That equation you asked about is just showing the time taken for the light ray to return to it's original position as



Then it uses that to prove that that time taken must be longer when its moving, as the hypotenuse is always the largest side

Its a proof of how time dilation actually works

Hint: Use the underscore to open a subscript

No clue what to do

[RuiAce]

No clue what to do

You'll pick up on it can always practice it under the guide

[owidjaja]

Hey guys!
Could someone please explain the Slingshot effect in relation to Newton's Laws of Motion and Universal Gravitation? I'm struggling how to formulate my response and integrate both concepts.

Thanks in advance

[fireives1967]

Hey guys, these holidays I've been studying for physics though I've been pretty worried that I'm using my time inefficiently. Since Physics is definitely more maths than content (or maybe I'm wrong) I feel like I should be practising calculations more rather than writing my syllabus notes.

What percentage or ratio do you guys recommend of how I should balance my Physics study?

80% Calculations 20% Content?
65-35?

[blasonduo]

Hey guys!
Could someone please explain the Slingshot effect in relation to Newton's Laws of Motion and Universal Gravitation? I'm struggling how to formulate my response and integrate both concepts.

Thanks in advance

Hey!!

As known, we use the slingshot effect to increase the velocity and change direction of the spacecraft to conserve fuel. The spacecraft is able to gain more kinetic energy through an elastic collision with the planet. Due to the law of conservation of momentum, which states that the total momentum of the two objects before the collision is equal to the total momentum of the two objects after the collision and thus:




Through this, we are able to see that if the velocity of the spacecraft increases, it's overall momentum increases and thus momentum from the planet must decrease. The planet's velocity decreases and because the mass of the planet is extremely large, the planet's velocity decrease is only very minute.

As the slingshot effect utilises the planet's gravitational field, the stronger this gravitational field strength, the more force can be placed on the spacecraft and the more velocity it can gain. Looking at the formula:



We can see that the smaller the distance between the objects and the larger the planet affects the force between the two objects and thus utilising a larger planet can give the spacecraft higher velocities

I hope this helps! Feel free to ask more!

Hey guys, these holidays I've been studying for physics though I've been pretty worried that I'm using my time inefficiently. Since Physics is definitely more maths than content (or maybe I'm wrong) I feel like I should be practising calculations more rather than writing my syllabus notes.

What percentage or ratio do you guys recommend of how I should balance my Physics study?

80% Calculations 20% Content?
65-35?

Hey!

This is a very difficult question to answer, as it really depends on how difficult you find the math components. However, most of the physics calculations in exams are just pulled directly out of the formula sheet and it becomes a simple substitute. Sometimes you'll need to "swap out" ie changing
F to ma. (you'll see these questions when practising, and you'll get used to it)

80% calculations, in my opinion, is way too much, some physics concepts do take a while to get down packed!  If you are struggling that much on calculations where you need 80% work on it, just keep asking questions until it sinks in

For me personally, I spent around 35% on calculations and 65% on content, which slowly decreased to about 15% calculations and 85% content right before the HSC exams.

As I said, it is different for everybody, and the main thing to do is work on the stuff you struggle with, and if that's calculations, then go for it.

[Aaron12038488]

i need help understanding the right hand grip rule, i find the right palm rule easy tho. Do we have to know how to use the right hand grip for M and G?