[d_94]

(Original post by sumzy101)
Yep as far as I have heard CIE BIo and Chem is easier than edexcel but when it comes to physics and maths...edexcel boeard is easier...

Reallyy!? Easier! Wow. Ughh. I just wanna get Edexcel over with :P

[EllaBella<3]

Hello

I was hoping somebody could explain to me how you prove/explain a glancing collision?

Thank you!

[Omar1994]

they can ask some really stupid questions sometimes that have nothing to do with the syllabus !

[d_94]

(Original post by Omar1994)
they can ask some really stupid questions sometimes that have nothing to do with the syllabus !

Truee

[lipton600]

Hey ,, anyone here kind enough to explain to me a question..UNIT 4
There's a past year question regarding electromagnetic induction ...about the bicycle wheel and the spokes moving in a clockwise direction..

I'm not sure what year is it from,,

(i) Label the hub and rim either plus or minus to show the polarity of the e.m.f.

Answer is HUB "-" and rim "+"...

I don't understand that,,, if you use flemings right hand,,, don't you get otherwise?

Thanks for taking time to read

[Parthenon93]

(Original post by lipton600)
Hey ,, anyone here kind enough to explain to me a question..UNIT 4
There's a past year question regarding electromagnetic induction ...about the bicycle wheel and the spokes moving in a clockwise direction..

I'm not sure what year is it from,,

(i) Label the hub and rim either plus or minus to show the polarity of the e.m.f.

Answer is HUB "-" and rim "+"...

I don't understand that,,, if you use flemings right hand,,, don't you get otherwise?

Thanks for taking time to read

Year and question no. please?

[Antimony]

(Original post by lipton600)
Hey ,, anyone here kind enough to explain to me a question..UNIT 4
There's a past year question regarding electromagnetic induction ...about the bicycle wheel and the spokes moving in a clockwise direction..

I'm not sure what year is it from,,

(i) Label the hub and rim either plus or minus to show the polarity of the e.m.f.

Answer is HUB "-" and rim "+"...

I don't understand that,,, if you use flemings right hand,,, don't you get otherwise?

Thanks for taking time to read

Basically use flems right hand rule where where you point first finger into paper, the thumb points to the right and the second finger points towards the positive polarity of the induced emf

I asked the same question :P follow the link for a full explanation
http://www.thestudentroom.co.uk/show....php?t=2013003

[Parthenon93]

(Original post by Antimony)
Basically use flems right hand rule where where you point first finger into paper, the thumb points to the right and the second finger points towards the positive polarity of the induced emf

I asked the same question :P follow the link for a full explanation
http://www.thestudentroom.co.uk/show....php?t=2013003

I am a bit confused. I used the right hand rule to get induced towards the rim. So shouldn't rim be negative? Isn't conventional current from positive end of battery to negative end of battery? :/

[Ifrahim]

Two loops, A and B, are aligned parallel to each other. There is a current in loop A, which induces a current in loop B. How does the current in loop A change with time?
guyssss need help with it.........

[Parthenon93]

(Original post by Ifrahim)
Two loops, A and B, are aligned parallel to each other. There is a current in loop A, which induces a current in loop B. How does the current in loop A change with time?
guyssss need help with it.........

Induced current in loop B should oppose the current in loop A. Also larger the current in loop A, larger the current in loop B - current in loop A is proportional to current in loop B. So I guess the current in loop A will fall exponentially with time.

[Killerstorm2]

(Original post by Parthenon93)
I am a bit confused. I used the right hand rule to get induced towards the rim. So shouldn't rim be negative? Isn't conventional current from positive end of battery to negative end of battery? :/

im confused about the same thing..

[iesians]

question for unit 5

why is a ball bouncing on a hard surface NOT an example of SHM ..?

[Parthenon93]

(Original post by iesians)
question for unit 5

why is a ball bouncing on a hard surface NOT an example of SHM ..?

Probably because the oscillation is damped. I am assuming it isn't isochronous either - time period not constant. So even though acceleration ∝ - displacement, it isn't a periodic motion.

For SHM you have two conditions: 1. periodic motion 2. a ∝ -x.

[Parthenon93]

(Original post by Killerstorm2)
im confused about the same thing..

Stongebridge cleared it up for me yesterday.

We are thinking of the stoke as a battery, but it is not.

In a battery the electrons are prevented from directly flowing through the battery - and so have to go externally through a wire.

In the stoke the electrons will flow internally through the stoke.

So the polarities appear opposite.

Since direction of induced current - i.e. direction of positive charge - is from hub to rim, the electrons must flow from rim to hub. The collection of electrons at the hub makes it negative.

[iesians]

(Original post by Parthenon93)
Probably because the oscillation is damped. I am assuming it isn't isochronous either - time period not constant. So even though acceleration ∝ - displacement, it isn't a periodic motion.

For SHM you have two conditions: 1. periodic motion 2. a ∝ -x.

WHAT ?!
almost every oscillation is damped !

[uuuuu]

in unit 4 when a capacitor charge's/discharges do the current and voltage or anything else also change

[DarrenDM]

Q10b

Shouldn't the bottom plate be - and top plate be +? (Not the other way round as stated in MS)

[cjcmoney]

(Original post by DarrenDM)
Q10b

Shouldn't the bottom plate be - and top plate be +? (Not the other way round as stated in MS)

The MS is talking about the molecules.... not the plates. the plates would be - on bottom and + on top but obviously the molecule - charge would be at the top attracted to the + plate

[DarrenDM]

(Original post by cjcmoney)
The MS is talking about the molecules.... not the plates. the plates would be - on bottom and + on top but obviously the molecule - charge would be at the top attracted to the + plate

Oh thanks! Misread it.

That's exactly what I thought, cheers.

[meraphox]

(Original post by Parthenon93)
Lol yes, but the oscillations you are considering are oscillations of very small amplitudes (4') and are only lightly damped by air.

Bouncing ball has very large amplitude (large height) and is heavily damped - I think about 1/3 or 2/3rd of the energy is lost every bounce.

But I could be wrong ofcourse.

No ur right I had a question like this in my m2 book and had to calculate loss in height for every bounce it followed a series pattern

It all depends on coefficient of restitution of the ball

Ie snooker balls are more elastic in collisions than tennis balls

But when bouncing them on the ground it's other way round

Ugh things like this bother me so much lol
Most of the marks these days depend whether you can interpret their writing in the way they want you to :/


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