# Principle of Relativity (Inertial/Non-inertial) (1 Viewer)

#### H4rdc0r3

##### Member
The question was 3 marks and was something like this.

How does the principle of relativity relate to inertial and non-inertial frames of reference.

I defined the principle of relativity as:
All steady motion is relative and there is no experiment you can perform to tell if you are in an inertial frame of reference, moving at rest or at constant velocity unless you have a reference to a point in another frame of reference.

I then said that principle of relativity applies to inertial frame of references only and it does not apply to non-inertial frame of references.

#### whitnall8

##### Member
thats what i said except i think they may have have been wanting implied knowledge of what a non-inertial frame is, so i think the word "accelerating" was needed

#### youngminii

##### Banned
Yeah I can't believe this was 3 marks
I wrote how Galileo came up with it (I dunno, fishing for marks)
Can't tell difference between a frame moving at constant velocity and stationary frame
This principle only applies to intertial frames of references

#### whitnall8

##### Member
I actually think that was one of the hardest questions to get full marks on because it was one of those "airy fairy" questions where you have to write exactly what they want you to write, otherwise you'll lose marks.

I think i may have lost a mark on that question

#### Ostentatious

##### jfK1c45g2f4Of56Eyd4f57cxZ
Same, I was thinking about writing that you couldn't tell you were in an inertial frame of reference but my experiment (holding a mass tied to a string in a moving bus) would be contradicted xD

Would my experiment be right though? As in, I am referring to the frame of reference of the mass?

#### whitnall8

##### Member
I think so. that's the experiment that i did, except i used a train. the frame of reference of the mass is basically the same frame of reference as the bus/train

#### Shoom

##### Member
Hey guys this is what I said.

I said the principle of relativ wateva says that an experiemnt cannot be carried out in an intertai frame of reference to determine your velocity ( aka wheter its constant or not), then I said you need to refer to another fram of reference to dtermine your motion, and gave an example.

Iss that right.

#### biopia

##### WestSyd-UNSW3x/week
This is something along the lines of what I said...

The principle of relativity states that measurements taken in one frame of reference are no more correct than another. This is referring explicitly to an inertial frame of reference as these FOR's are travelling at a constant velocity or are stationary. This means that no experiment can be carried out in an inertial frame of reference to prove that such a FOR is travelling at a constant speed or is stationary. A non-inertial frame of reference is one which is accelerating or decelerating. As such, a person can feel exterior forces acting on them thus proving the non-intertial state. Therefore, the principle of relativity does not hold in a non-intertial FOR.

I also put in something about how Newtonian laws apply in inertial frames of references, but I am not sure how correct that is. I only put it in there because I swear I read it on some concept cards before the exam :S

#### patrick little

##### New Member
I ended up writing about the thought experiment with the mirror where you would see your reflection in a frame of reference otherwise you would know you were moving and stuff... i forget the question fully

#### I.refuse.a.name

##### Member
- I wrote the speed of light is constant therefore mass/length/time are relative values
- No such thing as an absolute frame of reference (and hence no need for ether)
- Might have possibly mentioned relativity of simultaneity
- Something about an accelerating vs constant velocity/stationary frame
- Cannot determine whether in an inertial/non inertial frame without an external frame of reference

But I'm sure I rambled, I'm an Englishy person can't bring myself to dot point in an exam.

Darn, I wish there were more "airy fairy" questions because I prefer them - I feel they make you think and examine conceptual understanding but I can understand if you disagree because I hate the maths component and wished there were less equations this year so I just I have an opposite frame of mind.

Okily, sorry enough rambling

#### boganxcore

##### Member
i wrote about newtonian relativity and how it's impossible to perform a mechanical experiment to determine whether an inertial frame of reference was stationary or moving at a constant velocity. i may have wrote something brief about non-inertial (can't remember). i then wrote about the relativity of simultaneity and that if the speed of light is constant then mass, length and time are relative.

#### Ostentatious

##### jfK1c45g2f4Of56Eyd4f57cxZ
Yeah I also referred to the Special Theory.

#### whitnall8

##### Member
The Principle of Relativity is only Galileo's Theory, though. It has nothing to do with Einstein's Theory of Special Relativity

#### LauraHLH

##### Member
I described an experiment of holding a plumbob on a string while stationary, travelling at constand velocity and undergoing acceleration. Rambled on about how you can't discern between different inertial frames of reference (ie stationary vs constant motion) without having a non-inertial frame of reference. Not sure I did overly well, but hey. Nothing I can do now.

#### 00iCon

##### Member
I also put in something about how Newtonian laws apply in inertial frames of references, but I am not sure how correct that is. I only put it in there because I swear I read it on some concept cards before the exam :S
NEWTON'S FIRST LAW HOLDS!
This question was in Success One (idk if it was a past paper) and that's all it said. I remember going over the required amount of lines for this question, but I'm not sure exactly what I wrote.

#### Dx_God

##### Member
well basically principle of relativity states that all motion is relative, meaning that u can't state ur actual motion unless u got another external point and that u cannot tell upon whether ur at constant velocity or stationary in an inertial frame of reference. but however the motion itself is still relative to another external point and hence satifying the principle of relativity. for non-inertial frame of reference as though u would b probably able to tell tat u are accelerating but u still require another external point to make reference with. eg. though u might be accelerating to air particles but its perfectly possible to say ur not accelerating with respect to something else which has same acceleration as u and having the same instaneous velocity at a same point of time. therefore principle of relativity applies to both references. and plus u do realise that by "principle of relativity", ur dealing with GENERAL+SPECIAL relativity and that accelerated frame of reference is still inside it.(i'll give u a simple eg and u'll realise for sure. eg. questions to do with time dilation, mass contraction... and a rocket which is obviously in a non-inertial reference frame.)
[and i can't believe i screwed this question up in the exam lol and lost like 1-2 marks coz i mixed up inertial reference frame with non-inertial reference frame...wat a genius...never done that before in my life and the only time it happened was in the exam...*sigh*]

#### Dx_God

##### Member
and i don't really know what u guys are on about relating to newtonian physics and principle of relativity because that's not the question and to fully answer that question (relating to newtonian physics and principle of relativity) u need to talk about both general and special relativity which is way beyond hsc syllabus. [Most teachers and some mathmaticians got problems with general relativity coz of the high degree of math required to fully understand it (its in the uni physics course but even so u only learn it to a very shallow depth). thats why general relativity is not taught in high school and instead law of universal of gravitation is taught instead which is actually wrong when u consider extremities and its fixed by general relativity]
i'm sorry but if ur talking about newtonian physics in ur answers then ur abit off...just hope u stated the definition of principle of relativity and u might get 1 mark for it and 2 marks if u manage to write enough bs and the marker was in a good mood.

#### Dx_God

##### Member
but meh the bos will probably mark this question soft, i bet, coz not many in the state can get it perfectly correct. (correct to some extent maybe but i'm guessing mostly bs and not answering the question)