# A relativity question for a Physics teacher!

Discussion in 'Science' started by robbywilliams66, Nov 29, 2011.

1. ### robbywilliams66

Yes they would see each other.
The speed of light is independent of the speed of the source so when the light left rocket A it would be travelling towards rocket B at light-speed. Because rocket B is travelling at less than light-speed then the light would catch up with it.

2. ### physics_suits_you

Do you mind me asking about your qualifications / experience? Teaching Relativity is quite difficult and being corrected by my class on this would worry me.
Obviously, we all have to start somewhere but do you have someone to run through difficult ideas with you? Maintaining student confidence can be hard work and if I was a knowledgable parent, I'd be questioning your competence - sorry.

3. ### OrionNew commenter

Yeah tricky stuff, not to be done off the cuff
Sounds like A2 AQA sort of question for Unit 5D in which case I took a lot of stuff from here..
http://en.wikipedia.org/wiki/Inertial_frame_of_reference
There are lots of links which explain the AQA stuff quite well, just condense and use the exam questions to show the points.
Hope that helps!

4. ### jondclarke

Hi - surely there are always going to be questions that come up in class unexpectedly? Maybe that was the situation? I've always felt able to offer a tentative first opinion and/or say "I don't know" and an offer that we (both myself and the students) go away from the lesson and do some checking.
I support robbywilliams66's response.
If you'd like somewhere to run through difficult ideas, you're welcome to join talkphysics.org - we've got 5000 members happy to share teaching ideas, advice, etc.

5. ### physics_suits_you

I agree entirely, but trying to teach Special Relativity WITHOUT understanding the constancy of the speed of light seems incompetent to me. To have students correcting me on the basic concept of the lesson would only be acceptable if I wasn't really qualified to teach it and I'd been thrown in unexpectedly. I can imagine this person being a student, possibly with a degree in Engineering - nothing wrong with that BUT I would like my children to be taught by someone who knows their stuff. As you say, there is a lot of support available and perhaps this has highlighted a need for CPD in OP.
Before there were lots of boxes to tick, we used to do what was called "lesson preparation"!

6. ### MichaelellisNew commenter

Thanks to the teacher who answered my question. Can i ask physics_suits_you have you never been caught out by a question? what do you do? lie? Unfortunately I am the only physics teacher in the school and so my option for what I now see as an obvious answer was to come on here. I didn't expect my professionalism to be questioned and I am very angry that you think you can make judgements about me when you have absolutely no idea what my situation is. I came on to this forum in an open and honest way and now I wonder if I ever will again. Is this how you speak to your students? If so I would question your profesionalism.

7. ### physics_suits_you

I am happy to help you on this forum, as I help others. However, the correct way to get help is BEFORE you teach the kids. As I posted - this is lesson planning. I do not regard myself as infallible and have asked for help myself.
I feel sorry for you as the only physics teacher in the school; it is difficult. I know some schools do not even have a "physicist", but manage with the chemistry teacher doubling up. Whatever the situation, it is vital that teachers acknowledge what they don't understand and get help in advance.
From your comments, your class may have been ahead of you. Some of them had either read up on relativity (it IS an interesting topic) and understood your failure or quickly caught on from their independent study during the lesson. Hopefully this is the first time you have taught this work, as otherwise you have been leading previous pupils astray. THAT, in my eyes, is your "crime".You MAY now face a problem of students not trusting your knowledge; that is the price you pay for this.
Kids only get one proper chance at education and teachers owe them the best they can deliver. Yes, I've been caught out by questions and I agreed with jonclarke's post; I too have suggested tentative replies and an offer to find out. I NEVER lie (although I may be economical with the truth), and will ignore that slur.
I read your initial post as referring to a question YOU had asked. Special Relativity has only one basic tennet and that is the constancy of the speed of light, irrespective of the motion of the source or the observer. I can understand that you may not have covered this if your degree is not in physics (and I acknowledged that) but that is all the more reason why you need to "know what you don't know". If I caught a PGCE student going into lessons unprepared then I would speak to them harshly and accuse them of ignorance and arrogance: I expect the highest professional standards.
Think of ALL the things you need to know in order to teach projectile motion or electro-magnetic induction or field theory or just about any other part of the A level syllabus: that is when it is easy to get caught out. PLEASE prepare in advance and ask what you are not sure about.

8. ### missmunchieNew commenter

I think you are right. If you and I stood back to back and walked away from each other would we see each other? NO! If we did this at the speed of light or 2/3 the speed of light, what difference would it make? Obviously you class have no idea how rockets are designed, the fuel is expelled from the end making it inpossible to install a window! DUH!
Oh and rockets don't have eyes so they can't see. I think it is a trick question!

9. ### MichaelellisNew commenter

Thanks Miss munchie. I am going to use your reply (as a joke unless anyone thinks I am being serious!). Much more constructive than certain other ones I have had!

10. ### blazerStar commenter

I have occassonally been caoght out by a question. Two responses. The question becomes the HW! Then I get a couple of days to look it up. Or if a trivial question not related to the topic then I lie!

11. ### missmunchieNew commenter

I just realised I knew a Michael Ellis once, have you ever lived in Scotland?
It's much better to provide a simple answer rather than tie yourself up in knots I find!

12. ### OrionNew commenter

I think that maybe the issue is simply that everyone assumed that you were a Physicist and had taught post 16 before as in your first post you did not explain the background.

Maybe as well Physics teachers are fed up with Bio/Chem/ Unqualified people asking questions and teaching our subject - taking our jobs and not actually knowing the subject. It is not really their fault but those of the schools for giving them a job!

13. ### moodlebrook

I feel with michaelellis. I'm a Maths teacher and the only one who teaches Physics at my school although I'm not trained for it . There is virtually no prep time since we are understaffed and overloaded. Michael's experience is a constant nightmare of me although, touch wood, it hasn't happened to me (yet).

14. ### moodlebrook

The school hired me as a Maths teacher, my subject, only for me to be told at the beginning of the school year that I will also be teaching Physics since they didn't have anybody else to do it. Being under probation and needing the job what is one to do? I'd be much more comfortable doing my thing instead of "taking away" a qualified person's job.