# I have a tricky problem involving an electron and photon.

Dick
Homework Helper
You just stated 'where is the issue'. All the traditional formulas now have to be changed by multiplying by gamma.

And I wasn't sarcastic. Just flabbergasted at the way the physics community has dumbed-down.
I thought you were done. You promised. It's a frigging pedogical point. Many teachers of relativity feel that it causes more confusion than artificially preserving Newtonian expressions buys you. That's all. It makes the distinction between Newtonian mechanics and relativistic mechanics more explicit. It's the same damned theory. If you think this is 'dumbing down' you should probably take your flabbergastion elsewhere. It's just a change in the emphasis of notation.

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mfb
Mentor
To see how misleading it can be to try to keep Newtonian formulas:
No more F = d/dt (mv) (which was correct even relativistically)
m there now m(v), and in general F and dv/dt point in different directions - something really counterintuitive if you look at that equation. m is a scalar, but still the two vectors in that equation are not parallel to each other.

rude man
Homework Helper
Gold Member
To see how misleading it can be to try to keep Newtonian formulas:

... in general F and dv/dt point in different directions.
They do? News to me and I would think to Mr. Newton also.

- something really counterintuitive if you look at that equation. m is a scalar, but still the two vectors in that equation are not parallel to each other

It's counterintuitive that v and dv/dt can point in opposite directions? Like a car moving at v and letting up on the gas?

And what about centripetal force? Is it counterintuitive that v and dv/dt are non-parallel?

Guess I'm just not appreciating the New Order here - again.

Oh how things are changing in the world of physics since my day ... :grumpy:

@Dick - sorry, yes, I broke my word, but as long as I get ripostes I feel obliged to answer them. I promise not to initiate posts on this subject ever again.

mfb
Mentor
They do? News to me and I would think to Mr. Newton also.
Yes, I think special relativity would be new for Isaac Newton.
And what about centripetal force? Is it counterintuitive that v and dv/dt are non-parallel?
No, that formula does not uses vectors anyway (or you have to rewrite it - but v is squared anyway, so its direction does not matter).