My answers (not including long response) (5 Viewers)

[tashisthebest]

did anyone think that the rubber band question had like nothing 2 do with physics.
It wasn't 2 hard but i just think it was part of our syllabus

I do engineering studies and these sort of question come up in our engineering exams.

 

[slamduncs]

did anyone think that the rubber band question had like nothing 2 do with physics.
It wasn't 2 hard but i just think it was part of our syllabus

I do engineering studies and these sort of question come up in our engineering exams.

haha yeah. i also do engo studs and seeing that I laughed a bit in my head

 

[00iCon]

Or this guy could just explain it perfectly. Also with the B field:

Since the torque is only provided by side X (as it is the only side inside the field) you can use T=Fd.

F=BIL. so T=BILd. B=T/ILd. Which was 0.98.

Alternatively you can say that force of side X pushing down must equal that of the mass pushing down on Y. Hence (.04 x 9.8) = BIL

B=(.04x9.8)/(20x.2)=0.98T

Therefore, wrong, noob.

i did both to be sure!

did anyone think that the rubber band question had like nothing 2 do with physics.
It wasn't 2 hard but i just think it was part of our syllabus

I do engineering studies and these sort of question come up in our engineering exams.

I was almost ready to write on the paper: Thanks for giving us engineering students an unfair advantage!
But they look noting like conventional stress/strain curves!

 

[mR sinister]

most my answers are similare,
and i also got the same as you for the tourque t=fd
d = 0.3

To thecorey0 , i got the same frequency as you, yes frequency has too be quite big, since speed of light is soo large, and wavelengths are relatively small.

Also wasnt question 23) b = 34.5A , i found out the current in each conductor, then went reverse and found out the force, which was equal to the given value, so im 100% sure about this

Ohh and i might sound noob, but what do you type to get that box thingy of a previous post, so you can see which post you replied to

 

[Macdwg]

Fuck i think i got 34.5 A and i thought i was wrong, lets hope thats what i wrote down, fuck yeaa!!

 

[fuller45]

yeh i got around 35 A for the two wires one i think. So was the answer for the rock x or y?

 

[mR sinister]

I got X
pretty sure thats correct

 

[00iCon]

Ohh and i might sound noob, but what do you type to get that box thingy of a previous post, so you can see which post you replied to

LOL wot 4 n00bz0r!!!
u click on the button at the bottom of aforementioned post. the one that says "Quote"
otherwise use the [ quote ] and [ / quote ] tags without the spaces

 

[fuller45]

so electrons flow from the negative, through x, then around the back then through y? thats what i thought and yeah if you use the right hand palm rule then x moves up so it needs to be placed there. sweet. 1/100 woohoo!

 

[moke]

the mass is definetly placed on side x, n im not just saying that to prove how good i am. look at the guy's picture. use the three finger rule. index is field, it points away from the north pole since field direction is the direction of a north pole. current flows from positive to negative terminal so point the thumb down the page (remembering im using the guy's picture posted before). Finally that leaves your middle finger pointing upwards, out of the page. therefore that is the direction of the force. therefore to stop the rotor turning, the mass has to be placed on the same side X, to stop X from moving up.

Also, anyone who got A=34.5 is wrong and made this mistake.
I x I does not = 2I, it equals I squared. Therefore your answers were 69/2 = 34.5A when they should have been root 69 = 8.3A

 

[youngminii]

the mass is definetly placed on side x, n im not just saying that to prove how good i am. look at the guy's picture. use the three finger rule. index is field, it points away from the north pole since field direction is the direction of a north pole. current flows from positive to negative terminal so point the thumb down the page (remembering im using the guy's picture posted before). Finally that leaves your middle finger pointing upwards, out of the page. therefore that is the direction of the force. therefore to stop the rotor turning, the mass has to be placed on the same side X, to stop X from moving up.

Also, anyone who got A=34.5 is wrong and made this mistake.
I x I does not = 2I, it equals I squared. Therefore your answers were 69/2 = 34.5A when they should have been root 69 = 8.3A

You sir, just defeated half the people in this thread
I congratulate you

 

[mR sinister]

lol, forgive my noobness..
i didnt see the quote button even tho it is like the biggest button on the page.

 

[slamduncs]

My god. It is Y. I'll draw up a diagram after this game of HoN. At least I now know about 5% of the state got that one right, should help me push my rank up.

 

[moke]

My god. It is Y. I'll draw up a diagram after this game of HoN. At least I now know about 5% of the state got that one right, should help me push my rank up.

actually mate i think you'll find that 5% of the state got it wrong... i await your "all revealing" diagram...

 

[Macdwg]

the mass is definetly placed on side x, n im not just saying that to prove how good i am. look at the guy's picture. use the three finger rule. index is field, it points away from the north pole since field direction is the direction of a north pole. current flows from positive to negative terminal so point the thumb down the page (remembering im using the guy's picture posted before). Finally that leaves your middle finger pointing upwards, out of the page. therefore that is the direction of the force. therefore to stop the rotor turning, the mass has to be placed on the same side X, to stop X from moving up.

Also, anyone who got A=34.5 is wrong and made this mistake.
I x I does not = 2I, it equals I squared. Therefore your answers were 69/2 = 34.5A when they should have been root 69 = 8.3A

Mate, ull find that the right hand palm rule is actually with your fingers pointing in the direction of the field, which is left, and the palm pointing in the direction of the force. Sorry but try again? X is moving downwards.

 

[moke]

Mate, ull find that the right hand palm rule is actually with your fingers pointing in the direction of the field, which is left, and the palm pointing in the direction of the force. Sorry but try again? X is moving downwards.

i use a different rule but i can still see why you are wrong. the field is to the right. the direction of a magnetic field is the direction of force experienced by a small north pole. the bar magnet is a north end. therefore a north pole will be repelledto the right. so try your rule again with your fingers pointing to the right.

 

[darkchild69]

Conventional current is flowing into the page through side Y and out of the page through side X.

Magnetic field is running from left to right across the page

Using RHP rule, fingers pointing across the page, thumb pointing out of the page (for side X), experiences a force upwards.

Therefore the mass needs to be attached to this side to counteract the upwards force.

 

[Kakashi Hatake]

i use a different rule but i can still see why you are wrong. the field is to the right. the direction of a magnetic field is the direction of force experienced by a small north pole. the bar magnet is a north end. therefore a north pole will be repelledto the right. so try your rule again with your fingers pointing to the right.

i think for this question, the misunderstanding is that they did not place a south pole magnet on the other side of the coil so i'm not sure if we could say that magnetic field is to the right since there is one magnet being used.

 

[slamduncs]

http://img8.imageshack.us/img8/4543/pivotq.jpg

MSPaint ftw.

 

[emmjee92]

ok...i have a slight problem here!! i think i accidentally missed question 16. can someone plz help me out...what was q16??