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OCR PHYSICS B G494~ 11th June 2015 AM ~ A2 Physics

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Original post by Mutleybm1996

which paper?
how are you feeling about this exam?
any advice/tips?

June 2014.

Confident.

Advice/tips - remember the three points for all wordy BF questions and, actually, for all the energy/speed/ideal gas wordy questions - there will always be at least 1.

Reply 61

Nikeshp79

Been getting ~80% in past papers 2006-2014, but I know OCR will have something nasty in store for tomorrow so >_>

Reply 62

Mutleybm1996

Original post by DomStaff

June 2014.

Confident.

Advice/tips - remember the three points for all wordy BF questions and, actually, for all the energy/speed/ideal gas wordy questions - there will always be at least 1.

what are the "three points"?

Reply 63

Mutleybm1996

Original post by DomStaff

June 2014.

Confident.

Advice/tips - remember the three points for all wordy BF questions and, actually, for all the energy/speed/ideal gas wordy questions - there will always be at least 1.

what's 1/e? what's e?

Original post by Mutleybm1996

what's 1/e? what's e?

e is the base of the natural logarithm.

Reply 65

Rob-96

Original post by Mutleybm1996

what's 1/e? what's e?

1/e is about 0.37. So basically you can say that the time constant is the time taken for the current to fall to 37% of its initial value. e is just a special number that occurs in exponential relationships its about 2.718 to 4 sf.

Reply 66

Mutleybm1996

Original post by lizard54142

e is the base of the natural logarithm.

oh!
Yes I do maths so I know all about e, i thought it was referring to the charge on an electron and just thought "what?!"

with the graph, why is it everything to the right, i thought it was everything between R and D

and for the proof, can someone quickly explain what happens between the two highlighted lines? I'm quite a confident mathematician but it's bugging me as I keep ending up with ln(-lambdaN0) and you can't take logs of a negative number...

Original post by Mutleybm1996

with the graph, why is it everything to the right, i thought it was everything between R and D

It's everything to the right as potential is from infinity to a point so its from D to infinity.

Reply 68

Mutleybm1996

Original post by will_iredale

It's everything to the right as potential is from infinity to a point so its from D to infinity.

cheers

what about the second part? :smile:

Reply 69

Mutleybm1996

can someone briefly run through the highlighted lines? I didn't think you could take logs of a negative -lambdaN0???

highlighted.PNG5.0KB

Reply 70

will_iredale

Original post by Mutleybm1996

cheers

what about the second part? :smile:

I'm not entirely sure about the negative but i believe it's because -lamdaN0 is a constant so i just replaced it with C, took logs then put it back in at the end.

Reply 71

lizard54142

Original post by Mutleybm1996

can someone briefly run through the highlighted lines? I didn't think you could take logs of a negative -lambdaN0???

You could consider it as

ln| \lambda N_0 |

, which is just an arbitrary constant, which they have called

C

Reply 72

Mutleybm1996

Say you have gamma and the time taken for observers on Earth
How do you calculate the time taken for observers on a spacecraft?

Posted from TSR Mobile

Reply 73

urz13

Multiply it by gamma I think.

Good luck for today everyone - I can usually hit an A* on these papers but OCR have a habit of screwing us over so who knows what will happen...