ALL CIE PHYSICS DOUBTS HERE !!!

[Deadly_king]

Can sumone help me with diagrams in nov 2003 qp2, the first one is q3 (c) (i) just wanna make sure if its right and explain if you can pls,
the second one is q5 (c) why isn't it a straight line from origin, why  does it have a curve as it says on the mark scheme?
thanks so much for any help in advance

Nov 03 p2

3.(c)(i) In both strings the tension is directed towards the pulley. But I don't know how to explain it.

5.(c) Hmm...........first you should realize that it is a graph of velocity against distance from A.

Hence the gradient will be velocity/distance which is also equal to 1/time.

Therefore as the electron moves from A to B, time is increasing.

Since gradient = 1/time, an increase in time will lead to a decrease in gradient.

But velocity of the electron will be increasing due to the force of attraction from plate B and the force of repulsion from plate A.

Thus the graph should indicate an increase in speed while the gradient will be decreasing. This is why a curve is drawn instead of a straight line.

Hope it helps

[$!$RatJumper$!$]

Yeah, I understand what you mean. Once it was rather complicated for me too.

You should know this formula => Phase angle = 2(pie)/lambda

This formula applies when you have a graph of x against wavelength(lambda). Since in this case the graph is x against time(t), we can change the formula to => Phase angle = 2(pie)/T, where T is the period of oscillation and is the time difference.

It has been said that both waves have the same waveform, which implies same wavelength and same period. The only difference is that one would lead the other.

Take 2(pie) as 360^o since the phase angle has been given in degrees and not radians.
Hence 60^o = 2(180)/3 ---> =  0.5s

Therefore the new wave will lag behind by 0.5s, i.e it will have its first maximum at 0.5s and the first minimum at 2s.

Hope you get it.

Am sorry but I don't have any specific sites for this topic, but here are some links which a member has been so kind to look for us.

Excellent info. Thank you! +rep

[$!$RatJumper$!$]

What is the difference between the equations:

D*n*(lambda) / d

D*(lambda) / d

[Dania]

Do you mind drawing it out for me and uploading the pic? I get what you're saying. But I'm finding it hard to draw it. Thanks.

[Deadly_king]

Do you mind drawing it out for me and uploading the pic? I get what you're saying. But I'm finding it hard to draw it. Thanks.

Am sorry but I don't have a scanner

Nevertheless I'll see what i can do for you.

[Deadly_king]

What is the difference between the equations:

D*n*(lambda) / d

D*(lambda) / d

D(lambda)/d : It is the distance between the centres of two consecutive bright fringes or the distance between the centres of two consecutive dark fringes.

Dn(lamda)/d : It is the distance between the centres of two bright fringes which separated by n wavelengths or the distance between the centres of two dark fringes which are separated by n wavelengths.

But am not sure about the second one since it is only rarely used.

[Dania]

Am sorry but I don't have a scanner

Nevertheless I'll see what i can do for you.

You could take a picture with your phone, it doesn't have to be immaculate.

[Dania]

Help!
The mark scheme answer is so vague. I don't get it.

[TJ-56]

Nov 03 p2

3.(c)(i) In both strings the tension is directed towards the pulley. But I don't know how to explain it.

5.(c) Hmm...........first you should realize that it is a graph of velocity against distance from A.

Hence the gradient will be velocity/distance which is also equal to 1/time.

Therefore as the electron moves from A to B, time is increasing.

Since gradient = 1/time, an increase in time will lead to a decrease in gradient.

But velocity of the electron will be increasing due to the force of attraction from plate B and the force of repulsion from plate A.

Thus the graph should indicate an increase in speed while the gradient will be decreasing. This is why a curve is drawn instead of a straight line.

Hope it helps

Thanx for the help!
+rep

[Hypernova]

Do you mind drawing it out for me and uploading the pic? I get what you're saying. But I'm finding it hard to draw it. Thanks.

Here.

<a href="http://tinypic.com?ref=2wpqs09" target="_blank"><img src="http://i51.tinypic.com/2wpqs09.jpg" border="0" alt="Image and video hosting by TinyPic">[/url]

[Hypernova]

Help!
The mark scheme answer is so vague. I don't get it.

Understand that the weight of the body may be considered to act at its center of gravity. Weight is a force, so if it acts about a pivot it will cause a turning effect.
We know that the carboard comes to rest, therefore we conclude that there is no turning effect.

The only time there is no turning effect is when the weight acts through the pivot.
Think about it like this...moment=F*d...so if d=0,  then there is no moment.
The only force on it is weight, and weight acts through the pivot, then say there is no resulting moments.

[Deadly_king]

Understand that the weight of the body may be considered to act at its center of gravity. Weight is a force, so if it acts about a pivot it will cause a turning effect.
We know that the carboard comes to rest, therefore we conclude that there is no turning effect.

The only time there is no turning effect is when the weight acts through the pivot.
Think about it like this...moment=F*d...so if d=0,  then there is no moment.
The only force on it is weight, and weight acts through the pivot, then say there is no resulting moments.

Thank you very much dear member for your help

It's a real pleasure to have you here.

+rep

[Deadly_king]

Here.

<a href="http://tinypic.com?ref=2wpqs09" target="_blank"><img src="http://i51.tinypic.com/2wpqs09.jpg" border="0" alt="Image and video hosting by TinyPic">[/url]

That's exactly what I meant Dania.

[Dania]

Understand that the weight of the body may be considered to act at its center of gravity. Weight is a force, so if it acts about a pivot it will cause a turning effect.
We know that the carboard comes to rest, therefore we conclude that there is no turning effect.

The only time there is no turning effect is when the weight acts through the pivot.
Think about it like this...moment=F*d...so if d=0,  then there is no moment.
The only force on it is weight, and weight acts through the pivot, then say there is no resulting moments.

Thank You! That was very helpful.

[Dania]

Okay, so I seem to be stuck on (b) [Refer to the attachment]. Would I use the equation "Phase angle = 2(pie)x/lambda"?