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Physics: Post your doubts here!

G

geek101

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iKhaled said:
sorry that's the correct paper

http://www.xtremepapers.com/papers/CIE/Cambridge International A and AS Level/Physics (9702)/9702_w03_qp_2.pdf
Click to expand...
well 3 b is :
1) the sum of the forces in any direction must be zero
2) the sum of the moments of the force about a point must be zero
and if you mean 3 c ii....
1) quite simple...
M abut a point = force x perpendicular distance
= (30/100) x 150
= 45 Nm
2) it must be equal to the moments so it is also 45N
3) since the torque is 45Nm
and torque = one force x perpendicular distance
and we know that the perpendicular distance is 12/100 = 0.12 m
and the value of total torque is 45 Nm
so just substitute...
therefore Force = torque / perpendicular distance
= 45 / 0.12 = 375 N
The T is the mark scheme is tension which is the force caused by the string.
 
iKhaled

iKhaled

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geek101 said:
well 3 b is :
1) the sum of the forces in any direction must be zero
2) the sum of the moments of the force about a point must be zero
and if you mean 3 c ii....
1) quite simple...
M abut a point = force x perpendicular distance
= (30/100) x 150
= 45 Nm
2) it must be equal to the moments so it is also 45N
3) since the torque is 45Nm
and torque = one force x perpendicular distance
and we know that the perpendicular distance is 12/100 = 0.12 m
and the value of total torque is 45 Nm
so just substitute...
therefore Force = torque / perpendicular distance
= 45 / 0.12 = 375 N
The T is the mark scheme is tension which is the force caused by the string.
Click to expand...
sorry for wasting ur time, u explained the wrong question i meant 4 b iii..i am so sorry bro :/ thank u though .
 
angelicsuccubus

angelicsuccubus

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Jaf said:
Uh... no. That not how it will be.
1) It lags. That means any particular crest/trough will appear later in time. In your drawing, it appears earlier. Had it been a displacement-distance graph, the sketch would have been correct (almost (see below) ... :p )
2) Both, can't obviously start from A.

Here's a picture of my drawing:
View attachment 11098
Click to expand...
Jaf you're right about it not starting from the same point but otherise I don't agree with you... can you prove it somehow? I mean I get what you're saying that if it lags, it's slower and it should appear later.. but the wording of the question "lags behind T1 by a phase angle of 60 degrees" is concordent with my drawing.

Edit: you know what now Im just confused.. you might be right but I can't make up my mind.. need more opinions
 
angelicsuccubus

angelicsuccubus

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abcde said:
AoA! angelicsuccubus: I think you sort of misread the question. The answer requires a sketch of the same stationary wave 0.25 T later. There's no change in period. So the correct sketch would simply be a straight horizontal line (on the dotted line). leosco1995: In case you're confused, check this simulation: http://en.wikipedia.org/wiki/File:Standing_wave.gif :)
At t = 0s, the graph is as shown in the question
At t= 0.25 T, the graph is a straight horizontal line
At t= 0.5 T, the graph is again sinusoidal with the antinode 'crest' now being the 'trough' while the nodes remain exactly the same.
At t = 0.75 T, the graph is again a straight horizontal line
At t = T, the same graph as the question again.
(This only applies to a stationary wave. A progressive wave sketch is never horizontal at any time.)
Click to expand...
shoot me.. I should go sleep so I wouldnt do this in the exam.. sorry leosco1995
 
angelicsuccubus

angelicsuccubus

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Saad (سعد) said:
Okay...

In the syllabus, we have:

(e) describe the effect of a uniform electric field on the motion of charged particles.

And in the notes, I have things like Equipotential Surface, Potential Gradient, and 'Electric field lines must meet the surface at right angles'.

... What in the realm of Physics is this?
Click to expand...
lol that's A2 stuff you mentioned..
 
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geek101

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Question about the impulse....if there are two objects with the same mass and volume and moving with the same speed, one is hard and one is soft...what is the difference between the impulse of each?
 
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Famous4it

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Hi I have a few questions if someone could help me out, that would be great:
Can someone help me out with diffraction grating? That formula where you figure out the number of fringes.
2. how does the colour of the light and width of the slits affect the fringes (brightness, spacing)
3. And I read something about how when the slits are wider, intensity is less and so the fringes are darker. Is that right?
 
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