For energy change in mass-spring system:

elastic potential energy to kinetic energy to gravitational potential energy to kinetic to gravitational potential energy

Reply 84

mathsnerd000

for the question on work out the magnetic field strength of the copper wire, did have to times the force by number of electrons?

Because they said it was force for 1 electron

Reply 85

Sbarron

Original post by sour_lemons

I have never messed up so badly in an exam, i couldn't answer half of section B and usually I can get some kind of answer for calculations..but I didn't even know where to start. Section A was equally as bad, In past papers I rarely have to guess but I guessed at least 8 of them! No chance of uni now, i'll be lucky if I got 40 on that paper and I need an A!

Snap snap snap snap.... Ive been in tears... I guess its another year now to resit this!! :-(

Reply 86

mathsnerd000

what direction was the force acting on the electron in the wire?

Vertically up or vertically down

Reply 87

wofldog

Original post by mathsnerd000

what direction was the force acting on the electron in the wire?

Vertically up or vertically down

I said vertically down. Just about the only question on the paper I wasn't certain about.

Reply 88

abdcefghi

Original post by wofldog

I said vertically down. Just about the only question on the paper I wasn't certain about.

This is a troll surely :P?

Reply 89

username536618

Well that was pretty ****. I ran out of time to go back and try some tricky questions I missed out :/ hopefully next weeks goes well to compensate for this major fail...

Reply 90

wofldog

Original post by abdcefghi

This is a troll surely :P?

Nope!

Reply 91

SamPh

Do you think it would've been fine saying into the page if i said that the field was acting down and current to the right?

Reply 92

Geesus2512

Original post by KingSolomon

No that question is 23...not sure why he said it's 24

apologies i meant 23... 24 was to do with magnetic flux and emf i think?

Reply 93

Geesus2512

Original post by SamPh

Do you think it would've been fine saying into the page if i said that the field was acting down and current to the right?

yes. magnetic field acting south (down) current right thus force vertically down/into the plane - both should be accepted

Reply 94

KingSolomon

Original post by Geesus2512

yes. magnetic field acting south (down) current right thus force vertically down/into the plane - both should be accepted

Yep I believe I said south too.

Reply 95

Geesus2512

for the field strength did people get 0.155T?

Reply 96

Wobblybob76

I think I put vertically up, because the force on the current (positive charge) can be worked out using the left hand rule to be directed downwards. So I thought maybe the force on a negative charge would be upwards, but I'm not entirely sure :s-smilie: